E-ISSN 1471–0676 PLATINUM METALS REVIEW A Quarterly Survey of Research on the Platinum Metals and of Developments in their Application in Industry www.platinummetalsreview.com VOL. 50 JANUARY 2006 NO. 1 Contents Ruthenium Polyaminocarboxylate Complexes 2 By Debabrata Chatterjee, Anannya Mitra and G. S. De 10th International Platinum Symposium 13 Reviewed by R. Grant Cawthorn and A. J. Naldrett Mechanical Properties Data for Pt-5 wt.% Cu and 15 Pt-5 wt.% Ru Alloys By Kamili M. Jackson and Candy Lang An Overview of Supported Metal Catalysts 20 Reviewed by Neil R. McGuire Effects of Completely Encapsulating Platinum in Ceria 21 By David Thompsett and S. C. Edman Tsang 7th European Congress on Catalysis 22 Reviewed by Stephen Poulston, Andrew Smith and Thomas llkenhans Osmium – The Patent Landscape 27 By Richard Seymour Mechanisms of Volume Diffusion of Gold 29 into Single Crystal Iridium By S. M. Klotsman, S. A. Matveev, G. N. Tatarinova, A. N. Timofeev, A. V. Yermakov and V. K. Rudenko 2005 Nobel Prize in Chemistry 35 By V. Dragutan, I. Dragutan and A. T. Balaban The Ninth Grove Fuel Cell Symposium 38 Reviewed by Donald S. Cameron Abstracts 46 New Patents 50 Final Analysis: Improving Useful Service Life of Catalysts 52 By J. K. Dunleavy Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected]; Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE
Transcript
E-ISSN 1471–0676
PLATINUM METALS REVIEWA Quarterly Survey of Research on the Platinum Metals and
of Developments in their Application in Industrywww.platinummetalsreview.com
By Debabrata Chatterjee, Anannya Mitra and G. S. De
10th International Platinum Symposium 13Reviewed by R. Grant Cawthorn and A. J. Naldrett
Mechanical Properties Data for Pt-5 wt.% Cu and 15Pt-5 wt.% Ru Alloys
By Kamili M. Jackson and Candy Lang
An Overview of Supported Metal Catalysts 20Reviewed by Neil R. McGuire
Effects of Completely Encapsulating Platinum in Ceria 21By David Thompsett and S. C. Edman Tsang
7th European Congress on Catalysis 22Reviewed by Stephen Poulston, Andrew Smith and Thomas llkenhans
Osmium – The Patent Landscape 27By Richard Seymour
Mechanisms of Volume Diffusion of Gold 29into Single Crystal Iridium
By S. M. Klotsman, S. A. Matveev, G. N. Tatarinova, A. N. Timofeev, A. V. Yermakov and V. K. Rudenko
2005 Nobel Prize in Chemistry 35By V. Dragutan, I. Dragutan and A. T. Balaban
The Ninth Grove Fuel Cell Symposium 38Reviewed by Donald S. Cameron
Abstracts 46
New Patents 50
Final Analysis: Improving Useful Service Life of Catalysts 52By J. K. Dunleavy
Communications should be addressed to: The Editor, Susan V. Ashton, Platinum Metals Review, [email protected]; Johnson Matthey Public Limited Company, Hatton Garden, London EC1N 8EE
The chemistry of ruthenium complexes con-taining polyaminocarboxylate (pac) ligands (Ru-pac)is of continuing interest. The donor character ofthe pac ligand is comparable with that of manybiological enzymes which make use of the car-boxylate and amine donors from amino acids tobind to a metal centre. The pac ligand can formvery stable 1:1 (metal : ligand) complexes withruthenium.
Early studies (1-3), later confirmed by crystal-lographic evidence (4-8), showed that the pacligands in Ru-pac complexes function as pentaden-tate ligands, see Figure 1. The sixth coordinationsite of the ruthenium centre in Ru-pac complexesis occupied by a water molecule at low pH or by anhydroxide ion at high pH. Figure 1 shows struc-tures and formulae of some [Ru(pac)(H2O)]complexes, and Table I contains data on spectral,electrochemical and acid-dissociation constants forthese [RuIII(pac)(H2O)] complexes.
The chemistry of [RuIII(pac)(H2O)] complexesis dominated by their lability towards the aquo-substitution reaction, which affords a facile andstraightforward synthesis to mixed-ligand com-plexes (8). The reasons that ruthenium complexescontaining ‘pac’ ligands demonstrate potential
applications in metallodrugs are because of:• the number of stable and accessible oxidationstates they possess,• their rapid rate of ligand exchange, and• their ability to bind to certain biological mole-cules.
Furthermore, these Ru-pac complexes exhibitcatalytic properties, in homogeneous conditions inthe presence of oxygen atom donors, that mimicthe biological enzymatic oxidation of hydrocar-bons by cytochrome P-450 (8). Although thesignificance of Ru-pac complexes as chemothera-peutic agents has been reviewed (9), this articleaims to examine the prospects of Ru-pac com-plexes for promoting studies towards thedevelopment of Ru-pac based pharmaceuticals,for a range of diseases. A glossary of terms used inthe review is appended at the end of the paper.
The Ru-pac Complex as a Model forEnzymatic Oxidation
Dioxygen complexes of transition metals playan important role in a number of biological reac-tions. The formation of a Ru(IV)-peroxo complexspecies in the reaction of Ru(III)-edta and dioxygenwas first reported by Ezerskaya and Solovykh (10,
Platinum Metals Rev., 2006, 50, (1), 2–12 2
DOI: 10.1595/147106705X82874
Ruthenium Polyaminocarboxylate ComplexesPROSPECTS FOR THEIR USE AS METALLOPHARMACEUTICALS
By Debabrata Chatterjee* and Anannya MitraChemistry Group, Central Mechanical Engineering Research Institute, MG Avenue, Durgapur 713209, India;
and G. S. DeDepartment of Chemistry, University of Burdwan, Golapbag, Burdwan 713104, India
Ruthenium (Ru) complexes containing polyaminocarboxylate (pac) ligands (Ru-pac) havefeatures which indicate they may be suitable for biological applications. For instance, Ru-pac complexes can bind to biomolecules through a rapid and facile aquo-substitution reaction,and Ru-pac has a range of accessible oxidation states. Ru-pac also has some notable catalyticproperties that mimic enzymatic hydrocarbon oxidation by cytochrome P-450 in homogeneousconditions. This is of immense significance towards developing Ru-pac based agents foroxidative cleavage of DNA and artificial nuclease in DNA foot-printing experiments. Thisreview aims to highlight the scope of Ru-pac complexes as metallopharmaceuticals, andoutlines their potential for certain biological applications.
11) in the 1960s, while spectral, electrochemical,and kinetic evidence in favour of the formation ofthe [{RuIV(edta)}2(O2)]2- peroxo species during cat-
alytic hydrocarbon oxidation was reported by TaquiKhan and coworkers (12, 13). Ru-pac complexes(pac = edta, hedtra) in the presence of the single
Platinum Metals Rev., 2006, 50, (1) 3
Table I
Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H2O)] Complexes
Fig. 1 Schematic representation of ruthenium complexes [RuIII(pac)(H2 O)] bearing a pac ligand. The complexes aredepicted as in a low pH solvent, when the sixth coordination site is occupied by OH2. The coordinated H2 O moleculeis labile towards substitution reactions around this site
Hedta and Hpdta represent the protonated pendant COOH group in [RuIII(Hedta)(H2O)] and [RuIII(Hpdta)(H2O)], respectively. M is mol dm–3
oxygen atom donors: NaOCl, PhIO, t-BuOOHand KHSO5, were found to be active in catalysingthe epoxidation of olefins and the hydroxylation ofthe C-H bond (14, 15); both of these reactionsresemble enzymatic oxidation by cytochrome P-450 monooxygenase (an enzyme catalysingoxo-transfer reactions). Further, a system compris-ing [RuIII(edta)(H2O)]- /ascorbic acid/H2O2 (or O2)that was able to perform the hydroxylation ofcyclohexane to cyclohexanol, as an analogue of theUdenfriend system (16), was also reported (17).Ferryl intermediates (FeV=O) are the active DNAcleavage agents in O2-activated DNA cleavage bybleomycin. Bleomycin epoxidises stilbenes via itsferryl form. Similarly, [RuV(pac)O] was reported tobe the active species in the olefin epoxidation andhydroxylation of saturated hydrocarbons (14, 15a).Reports that the oxo-functionalisation of theC=C/C-H bond in hydrocarbon oxidation is catal-ysed by Ru-pac complexes seem to be highlysignificant for developing Ru-pac based agents foroxidative cleavage of DNA and artificial nucleasein DNA foot-printing experiments (15b).
Prospects for Ru-pac Complexes asAntitumour Agents
Although in cell culture studies a correlation hasbeen observed between the cytotoxicity of someruthenium complexes and their DNA binding abil-ity (18), the mechanism of the drug action of theseruthenium complexes is still largely unknown.Octahedral Ru(III) and Ru(II) complexes contain-ing ligands, such as ammines, N-heterocycles anddimethylsulfoxides, exhibited various degrees ofbiological activity, including antitumour action invivo (19). Considering that the above Ru(III) com-plexes are more inert than the correspondingRu(II) analogues, an ‘activation by reduction’mechanism was proposed to explain the antitu-mour activity of such complexes (19).
Ru-pac complexes, due to their lability towardsaquo-substitution, bind DNA constituents in afacile and straightforward manner (20-22) andthus have oncological significance. Antitumouractivity has been reported for labile Ru(IV)-cdta(cdta = 1,2-trans-diaminocyclohexan-N,N,N',N'-tetraacetate) (23, 24), while cis-[RuIII(pdta)Cl2] (pdta
= propylenediaminetetraacetate) is known to dam-age nuclear DNA and inhibit DNA recognition byenzyme restriction (25). A crosslinking with a gua-nine base unit of DNA has been proposed as anexplanation for the observed activity. However,the generation of a superoxide radical in NADPHoxidase, triggered by the presence of the Ru-pdtacomplex, may be another reason for the observedcytotoxity (9).
Mixed-ligand complexes of Ru(II)-pac with aseries of DNA bases have been reported byShepherd’s group (15c) and the binding sites of theDNA constituents have been discussed withregard to their significance in chemotherapy. Theyreported a novel η2-coordination mode for Ru-pac(pac = hedtra, ttha; ttha = triethylenetetraamine-hexaacetate) at the C5=C6 olefinic double bondsof uridine- and cytidine-related bases, along withcoordination at the normal binding sites (N3 andN1). Although the ‘pac’ environment favours π-donation by the ruthenium centre, no experimentalevidence for η2-attachment was observed in thecase of thymidine. This assumes the pyrimidinestructure is important for η2-coordination. Theaffinity of Ru(II)-pac complexes to the η2-pyrimi-dine site was shown to be linked to a balancebetween electronic and steric factors, and thus Ru-pac could be significant as a DNA crosslinkingagent (15c).
Our Ru-pac WorkIn our laboratory, kinetic and mechanistic
aspects of the interaction of [Ru(pac)(H2O)] com-plexes with DNA have been explored in attemptsto find mechanisms of possible drug activity. Ourprevious studies on the kinetics and mechanism ofbinding of [RuIII(edta)(H2O)]- with DNA bases,nucleosides and nucleotides, led us to concludethat [RuIII(edta)(H2O)]- binds an adenine base unitof single strand calf-thymus DNA in a kineticallypreferred pathway (20-22).
Other kinetic studies (26) have suggested thatthere is rapid coordination through the N7 of theadenine moiety of adenosine monophosphate(AMP) followed by a ring closure step in which theexocyclic NH2 group (at C6 in the adenine base) ofAMP binds to the ruthenium centre by dislodging
Platinum Metals Rev., 2006, 50, (1) 4
Platinum Metals Rev., 2006, 50, (1) 5
the adjacent carboxylate group of the coordinatedpac ligand, see Figure 2.
The order of reactivity of [RuIII(pac)(H2O)]complexes towards binding nucleotides is:
All the Ru-pac complexes exhibit a similar order ofreactivity towards nucleotides: AMP >> inosinemonophosphate (IMP) > guanosine monophos-phate (GMP).
The results of cell proliferation studies with Ru-pac complexes (26) using cell lines for MCF-7(breast cancer), NCI-H460 (lung cancer) and SF-268 (central nervous system) revealed that[Ru(edta)(H2O)]- and [Ru(pdta)(H2O)]- , are muchmore efficient inhibitors of these cell lines thancomplexes where pac = hedtra3- and medtra3- .[Ru(hedtra)(H2O)] and [Ru(medtra)(H2O)] haveinsignificant activity which, presumably, is associ-ated with a much lower rate of binding topurine-based nucleotides than in the case of the‘edta4- ’ and ‘pdta4- ’ complexes.
The order of growth inhibition for these threecancer cell lines, due to [Ru(edta)(H2O)]- is:SF-268 > NCI-H460 > MCF-7, and the estimated
GI50 values (in mM) of [Ru(edta)(H2O)]- are:0.57 for SF-268, 0.65 for NCI-H460 and 0.78 forMCF-7, respectively.
Furthermore, in cancer cells, binding of anactive agent with sulfur-containing biomoleculesavailable in the cells is considered to be one reasonfor ‘drug resistance’ and ‘toxicity’ of cisplatin-likedrugs in the postulated mechanism for activity(27). Binding with thio-macromolecules in the celldecreases the intracellular accumulation of metal-lodrugs, so they cannot reach sufficient numbersto bind with the DNA in the cell to cause celldeath. Thus it appears that understanding thekinetic interactions of these metal complexes withDNA fragments, with regard to sulfur-containingbiomolecules, is important for understanding theirantitumour activity as well as their toxicity.
We have recently reported that the binding rateof [RuIII(pac)(H2O)] with such thio-ligands ismuch lower than the binding rate with AMP (28).This indicates that Ru-pac complexes could have alower toxic effect, due to their lower reactivitywith sulfur-containing biomolecules, and thus beof pharmacological significance. Such possiblemetallodrugs could perhaps be tolerated at higherdosage with fewer side effects.
Fig. 2 Mechanism showing how [RuIII(edta)(H2O)] – binds an adenine base unit. The N7 of the adenine moiety ofAMP binds to the Ru-edta complex at the position where a COO – unit, coordinated to Ru, has been dislodged. kf is the forward rate constant of the reaction; kr is the backward rate constant of the reaction P is phosphosugar
kring closure
kf
kr
Ru-pac Complexes as NO ScavengersThe enzyme, nitric oxide synthase (NOS) catal-
yses the conversion of L-arginine to L-citrulline,during which reaction NO is produced (29). Thereare several isoforms of NOS and these are dividedinto the Ca2+-dependent constitutive NOS (cNOS)and the Ca2+-independent inducible NOS (iNOS)groups.
Effects of a Decrease in NONO seems to play a role in many disease states
(30a); for instance, a decrease in NO production(from cNOS) can lead to severe hypertension. Thisis a disease state that is treated by vasodilators (NOdonors), such as nitroprusside (30b). The route ofNO production from nitroprusside is:
[FeII(CN)5(NO)]3- → CN– + [Fe(CN)4(NO)]2- →NO + [Fe(CN)4(H2O)2]2- (ii)
The NO produced acts as:
NO → guanylate cyclase sites → GMP production →blood pressure control (iii)
Effects of Excess NOOn the other hand, sepsis and toxic shock are
caused in patients by the overproduction of NO –in response to a pathogenic invasion of the blood-stream (31-42). The result is a precipitous drop inblood pressure that could lead to multi-organ fail-ure, including renal failure. The excess NO in thebloodstream is present due to action bymacrophages (mononuclear phagocytic cells thatreside in tissues). This situation with the pathogensmay be treated by other antibiotics, while theexcess NO can be absorbed by a metal complexacting as a scavenger. Ru-pac complexes meet thebasic requirements for effective NO scavenging asthey undergo a rapid substitution reaction andform stable nitrosyl complexes (43). In addition,the Ru-NO bond is reasonably stable, and persiststhrough a variety of substitution and redox reac-tions. This allows the properties of the Ru-paccomplex to be finely tuned so it can become aneffective NO scavenger:
macrophage CAM cell → (pathogen/cytokine) →NO production (iv)
[RuIII(edta)(H2O)]- + NO →[RuII(NO+ )(edta)]- + H2O (v)
In vitro studies have shown that Ru-edta com-plexes are successful in scavenging NO inbiological systems and suggest that they could playa role in novel therapeutic strategies aimed at alle-viating NO-mediated disease states (44). Forinstance, the addition of Ru-edta complexes (100µM) to gamma-activated RAW 264 cells (a murinemacrophage cell line) was found to reduce NO lev-els. The effect of Ru-edta complexes onNO-mediated tumour cell killing by gamma-acti-vated macrophages (RAW 264) was studied in aco-culture system. A non-adherent murine masto-cytoma (P815) line was the ‘target’ cell. Ru-edtacomplexes (100 µM of JM1226 and JM6245) whenadded to the culture medium, gave some protec-tion from macrophage-mediated cell killing. The‘target’ cell viability increased from 54.5 ± 3.3% to93.2 ± 7.1% and 80.0 ± 4.6%, respectively, (n = 6).
The vasodilator response of isolated, perfused,precontracted rat tail arteries caused by a one-offinjection (10 µl) of S-nitroso-N-acetyl-penicill-amine (SNAP) was attenuated by adding Ru-edtacomplexes (100 µM) to the perfusate. The ED50
increased from 6.0 µM (Krebs only) to 1.8 mM(Krebs + JM6245) and from 7 µM (Krebs only) to132 µM (Krebs + JM1226). Male Wistar rats wereinjected with bacterial LPS (4 mg kg–1 intraperi-toneal of lipopolysaccharide) to induceendotoxaemia. When the JM1226 Ru-edta com-plex (100 µM) was administered 20 hoursafterwards, the LPS fully reversed the hypotensionassociated with the endotoxaemia.
A brief study of the kinetics of interaction ofRu-edta complexes with NO, aimed at under-standing the mechanisms of drug action (45),showed that the rate of the aquo-substitution of[RuIII(edta)(H2O/OH)]–/2– with NO is very fast(1.95–3.29 × 107 M–1 s–1 at 7.3ºC) in pH range6.5-8.0. However, at pH 8.0, the higher value forthe rate of aquo-substitution (3.29 × 107 M–1 s–1 at7.3ºC), than at pH 6.5 (2.18 × 107 M–1 s–1 at 7.5ºC),does not agree with the pH dependence of the rateconstants for the aquo-substitution reaction of the
Platinum Metals Rev., 2006, 50, (1) 6
Ru-edta complex with other entering nucleophiles(8). This apparently anomalous observation (45)could probably be explained by assuming the pK2
value for the acid-dissociation:
[RuIII(edta)(H2O)]– ↔ [RuIII(edta)(OH)]2– + H+
pK2 would, at 7.3ºC, be higher than the value (7.6)reported at 25ºC. As a result, the concentration ofthe generally labile [RuIII(edta)(H2O)]– specieswould be higher at low temperature (7.3ºC) evenat pH > 7.6. Therefore, the decrease in the rateconstant at pH > 7.6 reportedly observed for thesubstitution of Ru-edta complex at 25ºC was notseen at 7.3ºC by Slade et al. (45).
The thermodynamics and kinetics of Ru-edtacomplexes as efficient scavengers of NO wasrecently reported by Eldik’s group (46). Theresults of FTIR and 15N-NMR spectroscopy stud-ies clearly afforded evidence of the NO+ characterof NO coordinated to the Ru-edta complex. Thevalue of the overall equilibrium constant (KNO)determined from UV-Vis spectroscopic and elec-trochemical methods, is 9.1 × 107 M–1 at 25ºC andpH = 5.0. The effect of buffer components(acetate buffer) became clear, while the value ofthe rate constant (1 × 105 M–1 s–1 at 8ºC and pH5.0) was two-orders of magnitude less than thatreported by Slade et al. (45). An attempt to makedirect measurements of the rate of NO binding,using laser flash photolysis was unsuccessful,though the formation of a disubstituted[RuII(edta)(NO+ )(NO2
– )]2– was detected by 15N-NMR spectroscopy. Laser flash photolysis of thiscomplex was complicated by the number of chem-ical reaction steps.
In other recent reports, the preparation, char-acterisation, kinetics and biochemical activity ofvarious species of Ru-pac complexes (pac = edta;dtpa) were reported (47, 48). The report reaf-firmed the NO scavenging ability of Ru-paccomplexes and reported similar rate constant dataas Slade et al. for the Ru-edta complex (45).However, the binding of NO with Ru-dtpa wasslower (3 × 105 M–1 s–1 at 20ºC and pH = 7.4) (50mM phosphate buffer) than that observed for theRu-edta complex (45).
The reaction of [RuIII(edta)(H2O)]– with H2O2
in the presence of arginine produces NO, in theform of [RuII(edta)(NO+ )]–, and citrulline (49).This affords a simple model of NOS. A workingmechanism has been proposed for this reactioninvolving the hydroxylation of arginine by[RuV(edta)(O)]– species (formed by reaction of[RuIII(edta)(H2O)]– with H2O2) to resemble thefirst monooxygenase step of the NOS reaction(49). In a subsequent step, the oxidation of N-hydroxyarginine to citrulline and NO is proposedto take place via a ‘peroxide shunt’ mechanism(49).
Organ Rejection StudiesIn 2002 it was reported that NO derived from
the regulation of inducible NO synthase (iNOS)might play an important role in organ rejection(50). In experimental models of acute cardiactransplant rejection (without immunosuppres-sion), treatment using NOS inhibitors to preventacute rejection yielded conflicting results. This issuggested to be most likely due to potential inhibi-tion of constitutive NOS (cNOS). Accordingly,agents that trap NO directly may have someadvantage. The efficacy of the Ru-edta complexalone and in combination with low-dosecyclosporine (CsA, which is an immunosuppres-sive drug that delays graft rejection - a model ofdelayed graft rejection) for inhibiting the nitrosyla-tion of myocardial protein, and for prolongingcardiac allograft survival in a model of acute cardiactransplant rejection (without immunosuppression)has been evaluated (50). Treatment with the Ru-edta complex either prolonged the graft survivaland/or caused a marked decrease in myocardialnitrosylprotein formation, as determined by EPRspectroscopy. In vivo scavenging of NO by theruthenium complex was verified by high-perfor-mance liquid chromatography analysis of thenitrosylated drug in plasma samples. Low-doseCsA given alone or in combination with the Ru-edta complex completely blocked the formation ofmyocardial nitrosylprotein complexes. While low-dose CsA alone prolonged graft survival, thecombined therapy of CsA and the Ru-edta com-plex produced a synergistic effect on graft survival.The studies explored the possibility of using the
Platinum Metals Rev., 2006, 50, (1) 7
Ru-edta complex alone and in combination withCsA to protect myocardial proteins from post-transcriptional modification and to prolong cardiacgraft survival.
NO in Angiogenesis and TumourProgression
NO also plays a role in angiogenesis andtumour progression (51-62). These studies sug-gest that increased levels of NO correlate withtumour growth and spread in human cancers.Drugs that interfere in the nitric oxide synthase(NOS) pathway could thus be useful against angio-genesis-dependent tumours, and the RuIII-edtacomplex was found to be effective in this regard(62). The key steps of angiogenesis, endothelial cellproliferation and migration stimulated by vascularendothelial growth factor (VEGF) or NO donordrugs, were reportedly blocked by the RuIII-edtacomplex (62).
Ru-pac Complexes asProtease Inhibitors
Cysteine proteases (thiol protease in older liter-ature) have recently been discovered in viruses ofpoliomyelitis and hepatitis A (63, 64), and theirpathological role (65-69) in brain trauma, muscu-lar dystrophy, arthritis, cardiac ischaemia andAlzheimer’s disease is reasoned to occur via degra-dation of concerned proteins by the enzyme.Cysteine proteases have a control aspect on HIV-1, myocardial repair, periodontal disease andcytomeglavirus (herpes).
Recently, evidence from molecular, immunolog-ical and pharmacological studies has indicated thatcysteine cathepsins (peptidases belonging to thepapain family) play a role in the malignant progres-sion of human tumours (70). It has been suggestedthat cysteine cathepsins, most likely with serineproteases, degrade the extracellular matrix, therebyfacilitating tumour growth into surrounding tissuesand vasculature (70). Clinically, the levels, activitiesand localisation of cysteine cathepsins and theirendogenous inhibitors have been shown to havediagnostic and prognostic value (70).
In order to achieve selective inhibition of cys-teine proteases, cysteine protease inhibitor (CPI)
should have an active site which could, selectively,be highly reactive with the cysteine residue of theenzyme to produce an inert covalent enzyme-inhibitor complex. In this context, the use of metalcomplexes is conspicuously absent from the litera-ture. However, we have recently discovered thatRu-pac complexes possess cysteine protease inhi-bition activity (26, 71).
The protease inhibition activity of Ru-pac com-plexes was studied using three cysteine proteaseenzymes: bromalien, papain and ficin with azoal-bumin as the substrate. In order to understandcysteine protease inhibition by Ru-pac complexes,the interaction of Ru-pac complexes with cysteine(a thio-amino acid and cysteine protease containthis unit) and other thio-amino acids was studied,leading to the formation of S-coordinated species.The ability of Ru-pac complexes to inhibit cysteineprotease activity was attributed to the high affinityof the ruthenium complexes towards binding the–SH group in the cysteine residue of the enzymesvia a rapid aquo-substitution reaction. The proteaseactivity of the enzyme was thus inhibited by theformation of a stable Ru(edta)-enzyme complex,see Figure 3.
These studies demonstrate that the[RuIII(edta)(H2O)]– complex effectively inhibits theprotease activity of the three enzymes, whereas,the [RuIII(hedtra)(H2O)] complex, although able toreduce the hydrolysis of azoalbumin by bromaleinat a certain level, failed to do so with papain. Thelower efficacy of the Ru-hedtra complex, than theRu-edta complex, towards inhibiting proteaseactivity of bromalein may be linked with the loweraffinity of Ru-hedtra towards binding the –SHgroup in cysteine.
However, the absence of inhibition activity bythe Ru-hedtra complex for papain, and the signifi-cantly lower efficacy for ficin suggest that theprotease inhibition activity of the RuIII-pac com-plexes is enzyme specific.
Very recently it has been reported (72) that theS-atom of cysteine reacts to bind the N-atom ofthe nitrosyl complex of Ru-edta to form a 1:1intermediate species, which subsequently convertsinto another intermediate by reacting with anothermolecule of cysteine and ultimately produces
Platinum Metals Rev., 2006, 50, (1) 8
Platinum Metals Rev., 2006, 50, (1) 9
[RuIII(edta)(H2O]–. Cysteine is returned to thereacting system together with the release of N2O.This observation is of significance, implying thecatalytic reduction of NO to N2O in a biologicalsystem.
Concluding RemarksIn this article, we have primarily reviewed the
kinetics and mechanism of the interaction of Ru-pac complexes with biomolecules. The ability ofRu-pac complexes to perform hydrocarbon oxida-tion in a manner that resembles the enzymaticsystem, cytochrome P-450, appears to be usefulfor developing Ru-pac based agents for oxidativecleavage of DNA and artificial nuclease in DNAfootprinting experiments. The ability of Ru-paccomplexes to bind to DNA constituents at a fasterrate than to sulfur-containing ligands, pointstowards exploring the possibility of a new familyof ruthenium-based anticancer drugs of low toxic-ity. The [Ru(pac)(NO)] complexes offer a numberof features as NO carriers or scavengers.
The discovery of the protease inhibition activi-ty of Ru-pac complexes may be of significance indeveloping antiviral agents in which Ru-pac com-plexes could act as metallo-inhibitor agents fordisease progression.
Although the above features make Ru-paccomplexes promising for clinical application, abetter mechanistic understanding of the differentmodes of drug action of Ru-pac complexes wouldprobably yield more effective chemotherapeuticagents.
AcknowledgementDebabrata Chatterjee gratefully acknowledges the finan-
cial support from the Government of India (GrantSP/S1/F35/99). Anannya Mitra is thankful to CSIR for RA.
References1 T. Matsubara and C. Creutz, Inorg. Chem., 1979, 18,
19562 H. C. Bajaj and R. van Eldik, Inorg. Chem., 1989, 28,
19803 H. C. Bajaj and R. van Eldik, Inorg. Chem., 1990, 29,
28554 M. M. Taqui Khan, D. Chatterjee, R. R. Merchant,
P. Paul, S. H. R. Abidi, D. Srinivas, M. R. H.Siddiqui, M. A. Moiz, M. M. Bhadbhade and K.Venkatasubramanian, Inorg. Chem., 1992, 31, 2711
5 M. M. Taqui Khan, H. C. Bajaj, Z. Shirin and K.Venkatasubramanian, Indian J. Chem., Sect. A, 1992,31, 303
6 M. M. Taqui Khan, H. C. Bajaj, Z. Shirin and K.Venkatasubramanian, Polyhedron, 1992, 11, 1059
7 M. M. Taqui Khan, D. Chatterjee, S. Sanal Kumar,Z. Shirin, M. A. Moiz and S. D. Bhatt, Proc. IndianAcad. Sci. (Chem. Sci.), 1994, 106, 717
9 (a) M. J. Clarke, F. Zhu and D. R. Fraska, Chem. Rev.,1999, 99, 2511; (b) M. J. Clarke, Coord. Chem. Rev.,2002, 232, 69
10 N. A. Ezerskaya and T. P. Solovykh, Zh. Neorg.Chim., 1967, 12, 2922
11 N. A. Ezerskaya and T. P. Solovykh, Zh. Neorg.Chim., 1968, 13, 186
12 M. M. Taqui Khan, A. Hussain, G. Ramachandraiahand M. A. Moiz, Inorg. Chem., 1986, 25, 3023
13 M. M. Taqui Khan, M. R. H. Siddiqui, A. Hussainand M. A. Moiz, Inorg. Chem., 1986, 25, 2765
14 M. M. Taqui Khan, D. Chatterjee, R. R. Merchant,P. Paul, S. H. R. Abdi, M. R. H. Siddiqui, D.Srinivas, M. A. Moiz, M. M. Bhadbhade and K.Venkatasubramanian, Inorg. Chem., 1992, 31, 2711
CC PP s
O
O
N
N O O
R u
O
O
R
C P
S H
+
R
O
O 2 O H R u
O O N
N
O
O
Fig. 3 The protease activity of the enzyme, cysteine protease (CP) bearing an SH group, is inhibited by Ru-pac toform a stable Ru(edta)-enzyme complex. R is a peptidal unit that can recognise enzymes selectively. If R were known,then a reactive drug could be developed
15 (a) R. E. Shepherd, Inorg. Chim. Acta, 1993, 209, 201;(b) R. E. Shepherd, in “Trends in InorganicChemistry, Research Trends”, ed. A. Gayathri,Trivandrum, India, 1993, 3, 503; (c) R. E. Shepherd,Y. Chen, R. A. Krotes and M. S. Ward, Inorg. Chim.Acta., 2000, 303, 30
16 S. Udenfriend, C. T. Clark, J. Axelrod and B. Brodic,J. Biol. Chem., 1954, 208, 731
17 M. M. Taqui Khan, R. S. Shukla and A. Prakash Rao,Inorg. Chem., 1989, 28, 452
18 D. Frasca, J. Ciampa, J. Emerson, R. S. Umans andM. J. Clarke, Metal-Based Drugs, 1996, 3, 197
19 G. Sava, in “Metal Compounds in Cancer Therapy”,ed. S. P. Fricker, Chapman & Hall, London, 1994,pp. 65-91
20 D. Chatterjee, H. C. Bajaj and A. Das, J. Chem. Soc.,Dalton Trans., 1995, 2497
21 D. Chatterjee, M. S. Ward and R. E. Shepherd, Inorg.Chim. Acta, 1999, 285, 170
22 D. Chatterjee, A. Mitra, M. S. A. Hamza and R. vanEldik, J. Chem. Soc., Dalton Trans., 2002, 962
23 S. R. Vilaplana, M. G. Basallote, C. Ruiz-Valero, E.Gutierrez and F. Gonzalez-Vilchez, J. Chem. Soc.,Chem. Commun., 1991, 100
24 R. A. Vilaplana, F. González-Vilchez, E. Gutierrez-Puebla and C. Ruiz-Valero, Inorg. Chim. Acta., 1994,224, 15
25 E. Gallori, C. Vettori, E. Alessio, F. Gonzalez-Vilchez, R. Vilaplana, P. Orioli, A. Casini and L.Messori, Arch. Biochem. Biophys., 2000, 376, 156
26 D. Chatterjee, A. Sengupta, A. Mitra and S. Basak,Inorg. Chim. Acta, 2005, 358, 2954
27 P. Pil and S. J. Lippard, ‘Cisplatin and RelatedDrugs’, in “Encyclopedia of Cancer”, ed. J. R.Bertino, Academic Press, San Diego, CA, 1997, Vol.1, pp. 392-410
28 D. Chatterjee, A. Sengupta, A. Mitra, S. Basak, R.Bhattacharya and D. Bhattacharyya, Inorg. Chim.Acta, 2005, 358, 2960
29 “Methods in Nitric Oxide Research”, eds. M.Feelisch and J. Stamler, John Wiley & Sons Ltd.,Chichester, West Sussex, U.K., 1996
30 (a) S. P. Fricker, Platinum Metals Rev., 1995, 39, (4),150; (b) S. P. Fricker, in “Metal Ions in BiologicalSystems”, eds. A. Sigel and H. Sigel, Marcel Dekker,New York, 1999, Vol. 36, p. 665
31 M. Stefanovic-Racic, J. Stadler and C. H. Evans,Arthritis Rheum., 1993, 36, 1036
32 I. I. Singer, D. W. Kawka, S. Scott, J. R. Weidner, A.R. Mumford, T. E. Riechl and W. F. Stenson,Gastroenterology, 1996, 111, 871
33 Q. Hamid, D. Springall, J. Polak, V. Riveros-Moreno, P. Chanez, J. Bousquet, P. Godard, S.Holgate, P. Howarth and A. Redington, Lancet, 1993,342, 1510
34 S. P. Fricker, Expert Opin. Invest. Drugs, 1999, 8, (8),1209
35 S. Moncada, R. M. J. Palmer and E. A. Higgs,Pharmacol. Rev., 1991, 43, 109
36 (a) S. Moncada and E. A. Higgs, N. Engl. J. Med.,1993, 329, 2002; (b) J. F. Kerwin, J. R. Lancaster andP. L. Feldman, J. Med. Chem., 1995, 38, 4343
37 R. C. Bone, Ann. Intern. Med., 1991, 115, 45738 J. R. Parratt, J. Physiol. Pharmacol., 1997, 48, 49339 C. Thiemermann, Gen. Pharmac., 1997, 29, 15940 R. G. Kilbourn, S. S. Gross, A. Juburan, J. Adams,
O. W. Griffith, R. Levi and R. F. Lodato, Proc. Natl.Acad. Sci. U.S.A., 1990, 87, 3629
41 C. Thiemermann and J. Vane, Eur. J. Pharmacol.,1990, 182, 591
42 T. Evans, A. Carpenter, A. Silva and J. Cohen, J.Infect. Dis., 1994, 169, 343
43 M. M. Taqui Khan, K. Venkatasubramanian, Z.Shirin and M. M. Bhadbhade, J. Chem. Soc., DaltonTrans., 1992, 885
44 S. P. Fricker, E. Slade, N. A. Powell, O. J. Vaughan,G. R. Henderson, B. A. Murrer, I. L. Megson, S. K.Bisland and F. W. Flitney, Br. J. Pharmacol., 1997, 122,1441
45 N. A. Davis, M. T. Wilson, E. Slade, S. P. Fricker, B.A. Murrer, N. A. Powell and G. R. Henderson,Chem. Commun., 1997, 47
46 A. Wanat, T. Schneppensieper, A. Karocki, G.Stochel and R. van Eldik, J. Chem. Soc., Dalton Trans.,2002, 941
47 B. R. Cameron, M. G. Darkes, H. Yee, M. Olsen, S.P. Fricker, R. T. Skerlj, G. L. Bridger, N. A. Davis,M. T. Wilson, D. J. Rose and J. Zubieta, Inorg. Chem.,2003, 42, 1868
48 T. Storr, B. R. Cameron, R. A. Gossage, H. Yee, R.T. Skerlj, M. C. Darkes, S. P. Fricker, G. J. Bridger,N. A. Davis, M. T. Wilson, K. P. Maresca and J.Zubieta, Eur. J. Inorg. Chem., 2005, 2685
49 C. J. Marmion, T. Murphy and K. B. Nolan, Chem.Commun., 2001, 1870
50 G. M. Pieper, A. M. Roza, M. B. Adams, G. Hilton,M. Johnson, C. C. Felix, B. Kampalath, M. Darkes,Y. Wanggui, B. Cameron and S. P. Fricker, J.Cardiovasc. Pharmacol., 2002, 39, 441
51 O. Gallo, E. Masini, L. Morbidelli, A. Franchi, L.Fini-Storchi, W. A. Vergari and M. Ziche, J. Natl.Cancer Inst., 1998, 90, 587
52 K. Doi, T. Akaike, H. Horie, Y. Noguchi, S. Fujii, T.Beppu, M. Ogawa and H. Maeda, Cancer, 1996, 77,1598
53 L. L. Thomsen and D. W. Miles, Cancer MetastasisRev., 1998, 17, 107
54 G. M. Tozer, V. E. Prise and D. J. Chaplin, CancerRes., 1997, 57, 948
55 K. Doi, T. Akaike, H. Horie, Y. Noguchi, S. Fujii, T.Beppu, M. Ogawa and H. Maeda, Cancer, 1996, 77,(8), 1598
56 M. Ziche and L. Morbidelli, J. Neuro-Oncol., 2000, 50,139
57 D. C. Jenkins, I. G. Charles, L. L. Thomsen, D. W.Moss, L. S. Holmes, S. A. Bayliss, P. Rhodes, K.Westmore, P. C. Emson and S. Moncada, Proc. Natl.Acad. Sci. U.S.A., 1995, 92, 4392
Platinum Metals Rev., 2006, 50, (1) 10
58 L. L. Thomsen, J. M. Scott, P. Topley, R. G.Knowles, A. J. Keerie and A. J. Frend, Cancer Res.,1997, 57, 3300
59 M. Takahashi, K. Fukuda, T. Ohata, T. Sugimuraand K. Wakabayashi, Cancer Res., 1997, 57, 1233
60 L. C. Jadeski, K. O. Hum, C. Chakraborty and P. K.Lala, Int. J. Cancer, 2000, 86, 30
61 R. Pritchard, F. W. Flitney, M. A. Darkes and S. P.Fricker, VIIIth International Congress of theMetastasis Research Society, Sept. 2000, Clin. Exp.Metastasis, 1999, 17, (P108), 776
62 L. Morbidelli, S. Donnini, S. Filippi, L. Messori, F.Piccioli, P. Orioli, G. Sava and M. Ziche, Br. J.Cancer, 2003, 88, 1484
63 G. Kemp, A. Webster and W. Russell, EssaysBiochem., 1991, 27, 1
64 M. Allaire, M. M. Chernaia, B. A. Malcom and M. N.G. James, Nature, 1994, 369, 72
65 K. K. W. Wang and P.-W. Yuen, Trends Pharmacol.Sci., 1994, 15, 412
66 S. Kawashima, M. Nakamura and M. Hayashi, Biol.Chem. Hoppe-Seyler, 1990, 371, Suppl. 205
67 L. Joshua-Tor, H. E. Xu, S. A. Johnston and D. C.Rees, Science, 1995, 269, 945
68 M. Hugunin, L. Quintal, J. Mankovich and T.Ghayur, J. Biol. Chem., 1996, 271, 3517
69 H.-H. Otto and T. Schirmeister, Chem. Rev., 1997,97, 133
70 C. Jedeszko and B. F. Sloane, Biol. Chem., 2004, 385,1017
71 D. Chatterjee, M. S. A. Hamza, M. M. Shoukry, A.Mitra, S. Deshmukh and R. van Eldik, Dalton Trans.,2003, 203
72 F. Roncaroli and J. A. Olabe, Inorg. Chem., 2005, 44,4719
Platinum Metals Rev., 2006, 50, (1) 11
The AuthorsDebabrata Chatterjee joinedthe Central MechanicalEngineering ResearchInstitute (CMERI),Durgapur, India, in 1997,and is Head of theChemistry Group. TheInstitute is a consultantlaboratory under theCouncil of Scientific andIndustrial Research (CSIR),New Delhi. His majorresearch interests are in thedevelopment of ruthenium-based compounds forbioinorganic applicationsand in homogeneouslycatalysed hydrocarbon oxidations. He is also interested in thekinetics of bioinorganic reactions and the photocatalyticdegradation of organic pollutants. Childhood polio has left himphysically handicapped with a considerable mobility problem.
Dr Anannya Mitra is a ResearchAssociate in the ChemistryGroup of the CentralMechanical EngineeringResearch Institute. She iscurrently engaged indeveloping rutheniumcomplexes for biochemicalapplications.
Gauri Sankar De is SeniorProfessor of InorganicChemistry in the ChemistryDepartment, University ofBurdwan. His main researchinterests are kinetics andmechanistic studies of theinteractions of transition metalcomplexes with biochemicallyimportant nucleophiles.
Glossary
arginine is a nonessential amino acid in adults and supplies the amidine group for the synthesis of creatine.Arginine is also formed by the transfer of an N atom from aspartate to citrulline in the urea cycle. Arginine isimportant for NO production by the enzyme nitric oxide synthase. NO is important for maintaining cardiovascularhealth. However, most arginine is utilised in the liver and kidneys, and only a fraction is available for thispurpose.
citrulline, L-citrulline is a nonessential amino acid that supports the body in optimising blood flow through itsconversion to L-arginine and then, via nitric oxide synthase, to nitric oxide. Citrulline is synthesised in theintestinal tract from glutamine, and converts to arginine in the endothelial cells. Citrulline allows for increasedand sustained NO production in the endothelium to support circulatory function.
cytidine is a purine nucleoside: cytosine linked by its N9 nitrogen to the C1 carbon of ribose. It is a componentof ribonucleic acid (RNA) and its nucleotides are important in the synthesis of a variety of lipid derivatives.
Platinum Metals Rev., 2006, 50, (1) 12
effective dose 50, ED50, is the amount of drug required to produce 50 percent of the maximum response in apharmacological test. It is usually calculated from a plot of log(Dose) vs. response.
growth inhibitory concentration 50, GI50, is the concentration required to inhibit growth of tumour cells in an invitro test by 50 percent relative to a control.
JM1226, is now known as AMD1226, K[Ru(Hedta)Cl], potassiumchloro[hydrogen(ethylenedinitrilo)tetraacetato]ruthenate. A nitric oxide scavenger first developed at Johnson Matthey and now being further developed by AnorMED.
JM6245, is now known as AMD6245, [Ru(Hedta)(H2O)],aqua[hydrogen(ethylenedinitrilo)tetraacetato]ruthenium. A nitric oxide scavenger first developed at Johnson Matthey and now being further developed by AnorMED.
lipopolysaccharide, LPS also known as endotoxin, is composed of lipid and polysaccharide moieties. LPS is acomponent of the cell wall of gram-negative bacteria that is released from dying bacteria and stimulates many ofthe innate immune responses, including synthesis of nitric oxide. Lipopolysaccharide from Escherichia coli is acommonly used immune cell activator in laboratory immunology.
macrophage is a mononuclear phagocyte found in tissues, and plays an important role in the innate andadaptive immune response. Macrophages are produced from stem cells in bone marrow which develop intomonocytes, enter the blood, and later into tissue where they develop into macrophages. Macrophages killingested microorganisms. They can be activated by endotoxin and cytokines such as γ-interferon.
NADPH is nicotinamide adenine dinucleotide phosphate (reduced form).
nucleoside is a heterocyclic nitrogenous base, a purine or pyrimidine, in a N-glycosidic linkage with a pentosesugar. It is often used to denote a compound obtained by hydrolysis of nucleic acids, a purine or pyrimidinelinked to ribose (in RNA) or deoxyribose (in DNA).
nucleotide is a phosphate ester of a nucleoside, particularly the 5´-phosphate of a pyrimidine or purine in N-glycosidic linkage with ribose or deoxyribose, as occurs in the nucleic acids, RNA and DNA, respectively.
pyrimidine is a metadiazine, C4H4N2, which is the fundamental form of the pyrimidine bases. There are mostlyoxy or amino derivatives, for example, 2,4-dioxypyrimidine is uracil, 2-oxy-4-aminopyrimidine is cytosine, and2,4-dioxy-5-methylpyrimidine is thymine. Uracil, cytosine and thymine are constituents of nucleic acid.
RAW 264 cells are a murine macrophage cell line. RAW 264 can be activated with LPS to produce cytokines andnitric oxide.
SNAP is S-nitroso-N-acetyl-D,L-penicillamine, an organic nitric oxide donor molecule.
thymidine is a pyrimidine nucleoside, thymine linked by its N1 nitrogen to the C1 carbon of deoxyribose. It isone of the four nucleotides that make up DNA.
uridine is a pyrimidine nucleoside, uracil linked by its N1 nitrogen to the C1 carbon of ribose. It is a componentof ribonucleic acid (RNA), and its nucleotides participate in the biosynthesis of polysaccharides and somepolysaccharide-containing compounds.
Platinum Metals Rev., 2006, 50, (1), 13–14 13
Every four years, geologists from academia,national geological surveys, exploration and min-ing companies, interested in the platinum groupelements (PGE) hold an international symposiumto discuss the latest geological ideas, explorationtargets and technical information. However, onlythree years separated the 9th meeting held near theStillwater Complex in Montana, U.S.A. (1), and the10th meeting held in August 2005 in Oulu, Finland(2), perhaps reflecting the interest in these com-modities. The main organisers of the meeting wereTuomo Alapieti (University of Oulu) and MarkkuIljana (Geological Survey of Finland). As Finlandand western Russia have been centres of intenseexploration for platinum during the last few years,Oulu was an interesting locale for the meeting.
As always, there was a variety of presentations(totalling over 200) covering discoveries and eval-uations of mineralised areas, descriptions of thehost rocks (usually layered igneous intrusions),characterisations of different platinum-group min-eral assemblages, and ideas on the processes thatinduce platinum mineralisation.
What is new are the changes in reporting onexploration programmes to stock exchanges. Thishas meant that much more quantitative informa-tion is available about PGE developments thanever before. Unlike previous Platinum Symposia,exploration companies are now keener to reporttheir results, and give ore body models. Manyinteresting areas were described, but none that isgoing to change the future of PGE mining (3).
The Baltic ShieldStarting in Finland and Russia (geologically
called the Baltic Shield), many ancient intrusionscarry some PGEs and copper-nickel (Cu + Ni) sul-fides. Important resources occur in the PortimoComplex (over 200 Mt at 2 g t–1 Pd + Pt + Au),Koillismaa, Penikat and Keivitsa Complexes.
Despite drawbacks of variable grade and lack oflocal smelter, North American Palladium is inter-ested in continuing exploration in these areas. Manyother intrusions have been incompletely evaluated.
The Burakovka intrusion lies in western Russia,and at 720 km2 is the largest in Europe. Good min-eralisation occurs in a chromitite layer (like theUG2 in the Bushveld Complex) and at other levelsin the igneous intrusion. Another large, butdeformed intrusion, the Monchegorsk intrusion(550 km2 ), contained a high-grade, vein-like Ni-Cusulfide-rich system, largely mined out, but now hasbeen found to host two PGE-enriched layers withsignificant tonnage, although continuity of graderemains to be demonstrated. The Fedorova-Panaintrusion has a strike length of 40 km and thicknessof 3.5 km. A thick mineralised zone up to 50 mwide, allegedly like the J-M Reef of the StillwaterComplex, has been traced for 1.4 km. Grades arequoted at 2–10 g and up to 0.5% Cu + Ni, butresource tonnages were not given.
Unlike these layered examples, the Keivitsabody is a massive ultramafic plug, 3 by 4 km, witha central ore body of 1 km2, extending to at least500 m depth. It has a resource of 315 Mt at 0.5%Cu + Ni and 0.2 g t–1 PGE.
Canadian OccurrencesA jump to describing occurrences in Canada
may seem a long way, but geological evidence waspresented that Fennoscandia (Baltic Shield) andOntario/Quebec (geologically called the SuperiorProvince) were once joined before very ancientcontinental drift separated them over 2 billionyears ago. Many small layered intrusions in thatpart of Canada may be part of the same igneousevent as those just described. Examples, such as theRiver Valley intrusion ( 25 Mt at 1.4 g t–1 Pd + Pt +Au) and the Shakespeare intrusion with a 14 kmstrike length and 7 Mt at 0.8% Cu + Ni and 1g t–1
DOI: 10.1595/147106705X82405
10th International Platinum SymposiumPLATINUM-GROUP ELEMENTS – FROM GENESIS TO BENEFICIATION AND ENVIRONMENTAL IMPACT
Reviewed by R. Grant Cawthorn* and A. J. NaldrettSchool of Geosciences, University of the Witwatersrand, PO Wits, 2050, South Africa; *E-mail: [email protected]
PGE were documented. While such tonnages maynot seem large, the occurrences are near Sudbury,and may be able to take advantage of the proximi-ty to Sudbury’s mining and smelting infrastructure.
Exploration in Sudbury was (to our minds) themost important in terms of significant and proba-ble further ore exploitation. Despite its geographiclocation, it is 600 m years younger than the previ-ously described occurrences in the Baltic/Superiorsupercontinent. The deeper, distal, Cu-rich sul-fides, with relatively higher PGE, have beenknown for a long time, but exploration pro-grammes seem to be getting better at finding theirtargets, and a number were described (for example,McCreedy West and Podolksy). Tonnages werenot given, but grades of up to 10 g t–1 were com-mon. A smaller high-grade occurrence on the eastrim has 13 Mt at 5% Cu + Ni and 4 g t–1 PGE.Particularly interesting are aureoles of low-sulfidebut high-PGE mineralisation that have not beenfully appreciated until recently. They have beenrecognised around some of the distal, sulfide-richzones, and may exist around many more.
The Duluth Complex, on the shore of LakeSuperior, has been extensively explored. It has amarginal zone that is sparsely mineralised. It hasenormous but low-grade Cu, Ni and PGEdeposits. Extraction by leaching of the metals isbeing developed, and is considered viable.
New DiscoveriesA Ni-Cu-PGE discovery was reported from
Western Australia. The Nebo and Babel intrusionsare mafic rather than ultramafic and have a thickmineralised layer near their centre. Tonnages and
grades are: 400 Mt, 0.6% Cu + Ni and 0.2 g t–1
PGE. Somewhat similar is the remote FergusonLake deposit in Canada. A deformed gabbroicsheet, 14 km long by 500 m thick has a sulfide-richzone, 60 Mt at 1% Cu+Ni and 1.5 g t–1 PGE. Alower unit, poorer in sulfides, but richer in PGE,has recently been identified.
BrazilA Brazilian intrusion, Serra da Onca, was
described. It is extensive (25 km), with an ultra-mafic lower half and gabbroic upper half, like theBushveld Complex. Near and above the boundaryis a thick zone (200 m) with elevated PGE values,but generally not exceeding 1 g t–1.
SummariesNew PGE information from the traditional
areas: Bushveld, Noril’sk, Great Dyke andStillwater, was sparse, except for the Platreef,about which one compilation suggested resourcesof 600 Mt with grades from 1 to 2.5 g t–1. In termsof this tonnage, all the other occurrences men-tioned above are dwarfed into insignificance. In allrecent reports of explorations, base metals havebecome an important component of any possibleresource estimate, and it is anticipated that in thefuture exploitation will depend upon both pre-cious- and base-metal extraction. Perhaps onegeneral important observation about all theseoccurrences is that palladium exceeds platinum.
References1 R. G. Cawthorn, Platinum Metals Rev., 2002, 46, (4), 177 2 http://platinumsymposium.oulu.fi/3 R. G. Cawthorn, S. Afr. J. Sci., 1999, 95, 481
Platinum Metals Rev., 2006, 50, (1) 14
Tony Naldrett emigrated to Canadafrom the U.K. in 1957. In 1967 hejoined the Department of Geology,University of Toronto, retiring in1998. He is a Professor Emeritus,continuing to research magmaticsulfide deposits. His most recentbook is “Magmatic SulfideDeposits: Geology, Geochemistryand Exploration”, Springer-Verlag,2004. In 2002 the Society ofEconomic Geologists awarded himthe Penrose Gold Medal. He iscurrently an Honorary Professorin the School of Geosciences,University of the Witwatersrand.
Grant Cawthorn was born inEngland. He has geology degreesfrom Durham and EdinburghUniversities. After a post-doctoralfellowship in Newfoundland, henow teaches igneous petrology inthe School of Geosciences at theUniversity of the Witwatersrand,South Africa. His main interestslie in the formation and vastreserves (Pt, Cr, V) of theBushveld Complex. His Universitypost is supported by the miningindustry, and he holds the title ofthe Platinum Industry’s Professorof Igneous Petrology.
The Authors
Platinum-5 wt.% copper (Pt-5% Cu) and plat-inum-5 wt.% ruthenium (Pt-5% Ru) are widelyused alloys for platinum jewellery manufacture. Itis therefore surprising that their mechanical prop-erties are not well documented, as the mechanicalproperties of jewellery alloys are of fundamentalimportance in determining: (a) the ease with whichthe alloy may be formed into a jewellery item; and(b) the strength and durability of the finished itemin service. Knowledge of mechanical properties istherefore beneficial to both jewellers and materials’developers. Equally important is knowledge of the
processing and microstructural condition of thealloy for which data are quoted, but even whenmechanical property data are available, this infor-mation is often missing.
Some mechanical properties of pure platinum,Pt-5% Cu and Pt-5% Ru obtained from a review ofavailable literature are shown in Table I. It can beseen that hardness values are well documented formost conditions, probably because determinationof hardness involves a simple, non-destructive testwhich is quickly and easily carried out. However,while hardness testing is useful, it does not yield
Platinum Metals Rev., 2006, 50, (1), 15–19 15
DOI: 10.1595/147106705X93359
Mechanical Properties Data for Pt-5 wt.% Cuand Pt-5 wt.% Ru AlloysWORK PRESENTED AS A BASIS FOR FUTURE COMPARISONS
Kamili M. Jackson and Candy Lang*Centre for Materials Engineering, University of Cape Town, Rondebosch 7001, South Africa; *E-mail: [email protected]
Scant data exist for the mechanical properties of commercial platinum jewellery alloysPt-5 wt.% Cu and Pt-5 wt.% Ru. Here data from new evaluations are presented on 90% coldworked and fully recrystallised heat treated alloys at 800ºC. Recommendations are madefor procedures in reporting future evaluations including disclosure of full processing details.
Table I
Currently Available Mechanical Properties of Pt-5 wt.% Cu and Pt-5 wt.% Ru
Vickers hardness Ultimate tensile % Elongation Referencestrength, MPa at fracture
Pure PtAnnealed 40–50 117–159 30–40 1, 2, 5, 6Cold worked 100 234–241 2.5–3.5 2
* The amount of cold work is not specified in the reference; ? indicates no information is available
Platinum Metals Rev., 2006, 50, (1) 16
easily interpreted results. Hardness is related tostrength, ductility and elastic modulus, but theseproperties are not simply extracted from the hard-ness value. Conversely a properly conducted tensiletest is easily interpreted, and the yield strength,tensile strength, elastic modulus and ductility canbe more simply distinguished. For precious metalssuch as platinum, considerations of cost (tensiletest specimens being relatively large) probablyaccount for the paucity of tensile test data.
Table I also shows that most of the availableinformation is for the annealed and as cast condi-tions, which are expected to exhibit similar values.With the exception of Lanam and Pozarnik (4),very few sources give processing information suchas annealing temperature, or microstructural infor-mation, such as grain size. Also lacking areexperimental details that allow other researchers toevaluate the data.
In order to test platinum jewellery alloys, amicrosample tensile testing machine has been builtat the University of Cape Town that can test sam-ples of total length 8 mm. This paper reports onmeasurements of both the hardness and tensileproperties of Pt-5% Cu and Pt-5% Ru, in theannealed and 90% cold worked conditions. Theaim is to provide mechanical property values, aver-aged from multiple tests, from specimens forwhich detailed processing and microstructuralinformation is provided.
Experimental ProcedureAlthough there is a pressing need to measure
the mechanical properties of platinum alloys, it isnot a very practical undertaking when the expenseof the material is considered. Even the smallestspecimens in the ASTM tensile testing standards(7) are beyond the means of many researchers.The approach used here: microsample tensile test-ing, has been used previously for other materialswith success (8). It uses a very small sample that isas close to the ratios of the ASTM standard as pos-sible while minimising the amount of materialused. It is useful in this situation because it reducesthe cost of carrying out multiple tests to provideadequate data. A schematic of the specimen designcan be seen in Figure 1.
The specimen has a total length of 8 mm, witha nominal gauge width of 0.5 mm and a nominalgauge length of 2.26 mm. The thickness can bevaried by the amount that the starting plate isrolled and is kept of the same order as the width.Typically the gauge width contains 5 to 10 grainsbut this is obviously determined by grain size.
The custom built apparatus is shown in Figure2. A tensile specimen is positioned in the grips.The operation of the tensile testing apparatus isbased on a screw driven actuator that applies aload to the specimen in the grips. Friction isreduced to a negligible amount with an air bearing.Load is measured with a 500 N load cell and dis-placement is measured with a miniature linearvariable displacement transducer (LVDT) sensor.A computer records both displacement and load.Because displacement is not measured directly onthe specimen, we do not regard the elastic straindata as reliable; furthermore analysis of the elasticresponse is complicated by elongation of the spec-imen ends in the grips. However, the recordedplastic elongation is reliable and compares wellwith direct measurements made on the specimensafter testing. Examination of specimens after test-ing confirms that the plastic behaviour isconcentrated in the gauge section.
To make the tensile specimens a plate is firstrolled to the required thickness. If required, theplate is then annealed. This can take place beforeor after cutting. The cold worked specimens werecut with the tensile axis parallel to the rolling direc-tion. The samples were cut using both a computer
Fig. 1 Schematic of the small tensile specimen ready fortesting; all the dimensions are in mm
Platinum Metals Rev., 2006, 50, (1) 17
numerical control (CNC) mill and wire electro dis-charge machining. The choice of cutting methodwas found to have little effect on the materials.The Pt-5% Cu and Pt-5% Ru samples were mea-sured at two extremes of mechanical behaviour:the recrystallised and 90% cold rolled states.
Specific information about their processing is asfollows: the as received material was homogenisedfirst at 1000ºC for 12 hours. It was then cold rolledto 90% reduction in thickness. Half of the materi-al from each alloy was retained to perform testingof 90% cold rolled material. The remainder washeat treated at 800ºC for six hours under vacuum.Light micrographs of the grain structure were taken.Hardness and tensile specimens were polished to amirror finish for consistency. Small sample tensiletests and Vickers hardness tests with a 100 g loadwere performed with each set of specimens.
ResultsLight micrographs from each set of material are
shown in the figures. Figures 3 and 4 show themicrostructure of the materials in the 90% coldrolled and 800ºC heat treated conditions, respec-tively. As expected the 90% cold rolled materialshows grains that are elongated in the direction ofrolling. The heat treated Pt-5% Cu exhibits com-plete recrystallisation, with equiaxed grains of size~ 100 µm. By comparison, the heat treated Pt-5%Ru alloy, Figure 4(b), shows finer grains, of size ~50 µm.
Figure 5 shows some typical tensile test results.As expected, the 90% cold rolled alloys exhibit ahigher yield stress and significantly lower ductilitythan the recrystallised alloys.
The calculated average results of tensile testsare seen in Table II along with the hardness results.
LVDT
Load cell Grips
8mm
Screw Driven Actuator
Air Bearing
Fig. 3 (a) Pt-5 wt.% Cu in the 90% cold rolled state and (b) Pt-5 wt.% Cu in the 800ºC heat treated condition
Fig. 2 The tensile testing apparatus with a specimen, of eitherPt-5 wt.% Cu or Pt-5 wt.% Ru held in the grips. The 8 mm longspecimens used in the tests are produced by rolling
(a) (b)
Platinum Metals Rev., 2006, 50, (1) 18
It can be seen that the two alloys are not signifi-cantly different in strength, however, the Pt 5%Cu alloy is more ductile than the Pt 5% Ru alloy.
DiscussionIf the new data in Table II is compared with the
literature values quoted in Table I, it can be seenthat the hardness and strength values obtained inthe present work are consistently higher. This isexpected for the cold rolled specimens, since thevalues obtained from the literature were for 50%cold worked alloys, and the results in the presentwork are for 90% cold work. The increased dislo-cation density in the 90% cold rolled specimensresults in higher values for both hardness andstrength, and very low ductility.
The difference in values for annealed speci-
mens quoted in the literature and in the presentwork should also be evaluated on the basis ofmicrostructure, but unfortunately heat treatmentand microstructure data are not available for thevalues in the literature. The light micrographs inFigures 3 and 4 show that Pt-5% Ru has a finergrain structure than the Pt-5% Cu after heat treat-ment at 800ºC. This suggests that the recrystal-lisation temperature of Pt-5% Cu is lower thanthat of Pt-5% Ru, consistent with the slightlylower melting temperature of Pt-5% Cu. Therecrystallisation temperature for both materials isclearly 800ºC or less after 90% cold work, and iscertainly less than the 1000ºC after an unspecifiedamount of prior cold work suggested in (3). Thehardness and strength values in Table II show thatthe values for Pt-5% Ru are higher than for Pt-5%
Fig. 4 (a) Pt-5 wt.% Ru in the 90% cold rolled state and (b) Pt-5 wt.% Ru in the 800ºC heat treated condition
Fig. 5 Tensile stress-strain curves from Pt-5 wt.% Cu and Pt-5 wt.% Ru alloys
Pt-5% Cu 90% cold rolledPt-5% Cu recrystallisedPt-5% Ru 90% cold rolledPt-5% Ru recrystallised
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
ENGINEERING STRAIN
Cu after the same heat treatment, which can beexplained by the finer grain size of the Pt-5% Ru.Similarly, the difference in elongation may havemore to do with the difference in grain size ratherthan real differences in the alloys. This illustratesthe importance of both processing andmicrostructural information in evaluating mechan-ical property data.
The standard deviations of the strength datashown in Table II, illustrating the variation in val-ues obtained in repeated tests of the samespecimen type, are relatively large at around 10%.This underscores the necessity of carrying out mul-tiple tests on each specimen type in order to obtainreliable average values for mechanical properties.
ConclusionThe results presented provide data to serve as a
basis for comparison in further research on plat-inum alloys. It has been shown that the two mostwidely used platinum alloys are not significantlydifferent in mechanical properties, and in addition,microstructure information and hardness valuesfor each tested sample have been included. This isthe most comprehensive information available onmechanical properties of these alloys and can serveas a baseline for alloy development. It is recom-mended that published mechanical data shouldinclude full processing information, microstructur-al characterisation if possible, number ofspecimens measured, and standard deviation or
range of values obtained. This will greatly assist inevaluation of data and comparison with othermeasurements.
References1 E. Savitskii, V. Polyakova, N. Gorina and N.
Roshan, “Physical Metallurgy of Platinum Metals”,Pergamon Press, Oxford, 1978
2 K. H. Miska, ‘Precious Metals’ – Manual 264, Mater.Eng., 1976, 84, (5), pp. 65–71
3 “Metals Handbook”, 9th Edn., Vol. 2, ‘Propertiesand Selection: Non-Ferrous Alloys and Pure Metals’,ASM International, Materials Park, OH, 1984
4 R. Lanam and F. Pozarnik, Platinum GuildInternational, U.S.A., 1999, 3, (1), 1; http://www.pgi-platinum-tech.com/pdf/V3N1w.pdf
5 “An Introduction to Platinum”, Johnson Matthey,London, 1990, a manual of design and manufactur-ing processes, contact [email protected]
6 A. S. Darling, Int. Metall. Rev., 1973, 18, 917 Standard Test Methods for Tension Testing of
Metallic Materials, ASTM 370, E8-93, pp. 130–1498 D. A. LaVan and W. N. Sharpe, Exp. Mech., 1999,
39, (3), 210
Platinum Metals Rev., 2006, 50, (1) 19
Table II
Average Results from Tensile Tests, with Standard Deviation for Pt-5 wt.% Cu and Pt-5 wt.% Ru
* The figures in parentheses indicate the number of tests conducted to obtain each set of values
The Authors
Dr Kamili Jackson was a Post DoctoralFellow in the Department of MechanicalEngineering, UCT. Her work included thetensile testing of current and new platinumalloys for use in jewellery applications.
Candy Lang is Associate Professor in theDepartment of Mechanical Engineering at theUniversity of Cape Town (UCT). She is leaderof the Hot Platinum research project, whichis involved in developing novel platinumtechnology for thejewellery industry.
Platinum Metals Rev., 2006, 50, (1), 20–21 20
This book is Volume 5 in the open-ended“Catalytic Science Series”, dedicated to an in-depthdescription of catalysts and their extensive applica-tions. Prior volumes are: “Environmental Catalysis”,“Catalysis by Ceria and Related Materials”,“Zeolites for Cleaner Technologies” and “Isotopesin Heterogeneous Catalysis” (Volumes 1 to 4,respectively). “Supported Metals in Catalysis” pre-sents recent developments in characterisation andapplication of supported metals in heterogeneouscatalysis – a truly mammoth task for one publica-tion. While the book is not dedicated to the use ofplatinum group metal (pgm) catalysts, they do fea-ture throughout, reaffirming their vital role in theworld of heterogeneous catalysis.
As with many other publications on heteroge-neous catalysis, this book can be divided into threemain categories: preparation, characterisation andapplication. The first chapter describes the prepa-ration methods used in the manufacture ofsupported metal catalysts, namely impregnationand precipitation. Even though this chapter isbiased towards impregnation techniques, it pro-vides a useful insight into the design andoptimisation of catalysts prepared on various sup-port media (powder and monolith).
Chapters 3 and 4 concentrate on variousaspects of catalyst characterisation. The authorsadmit it would be impossible to describe in detail,in only a few chapters, all the methods used for thedetermination of the physical and chemical prop-erties of metal catalysts. However, the reader isprovided with a good foundation with which toexplore the range of spectroscopic techniquesavailable, with specific examples of their utilisationfor in situ characterisation of metal catalysts.Chapter 4 is worthy of particular mention, wheremethods used to determine dispersion and support
metal crystallite size are discussed. This subjectmatter has formed an integral part of many doc-toral theses, and many would have undoubtedlybenefited from reference to this book.
The remainder of the book is dedicated to spe-cific areas of heterogeneous catalysis, withcomprehensive reviews covering subject matter asdiverse as the catalytic activation of C1 com-pounds and the reforming of naphtha, to theproduction of hydrogen and synthesis of finechemicals. The catalytic abatement of pollutantsemitted from the flame combustion of fossil fuelsfor transport applications is also introduced. Itcould be argued that a much more in-depth inves-tigation than the book provides is required for acomprehensive understanding of the vast body ofresearch carried out in this particular field over thepast 30 years. However, for a relative newcomer tothis area, the subject matter is well introduced andencourages the reader to delve further into auto-motive catalysis, as, indeed, do all the othersections for their particular fields. In essence, suchencouragement forms the primary aim of this pub-lication, and in this it excels brilliantly.
Catalysts for the manufacture of fine chemicalshave been a major, and almost exclusive, focusthroughout my career, and I have had the pleasureof working alongside the authors of Chapter 9,who deal with this topic. Dr Richard Wells, now atthe University of Aberdeen, who advised methroughout my Ph.D., and my colleague, Dr PeterJohnston, whose pensmanship is recognisable,even under the name Peter Johnstone.
The greatest challenge posed by the fine chem-ical industry to catalysis is the need for ever-increasing selectivity to a desired product. Selectivehydrogenation alone warrants many chapters inthis series of books. In this volume, the authors
DOI: 10.1595/147106706X93916
An Overview of Supported Metal CatalystsSUPPORTED METALS IN CATALYSISEDITED BY JAMES A. ANDERSON and MARCOS FERNÁNDEZ GARCÍA, Imperial College Press, London, 2005, 368 pages, ISBN 1-86094-490-6, £48.00
Reviewed by Neil R. McGuireJohnson Matthey Catalysts, Orchard Road, Royston, Hertfordshire SG8 5HE, U.K.; E-mail: [email protected]
Platinum Metals Rev., 2006, 50, (1) 21
cover the much publicised hydrogenation of buta-diene and α,β-unsaturated carbonyl compounds,but I would encourage them (and those reading) toinvestigate further the role of heterogeneous cata-lysts in the selective hydrogenation of moleculescontaining functions such as aromatic rings, hete-rocycles, nitro groups and nitriles, halides andprotecting groups. Catalysts capable of selectivelyhydrogenating the aforementioned groups, in thepresence of others, are in high demand, and thepharmaceutical, agrochemical and fine chemicalindustries would value them greatly.
As Professor Geoffrey Bond states in the pref-ace, no single mind can fully comprehend theentirety of a subject as diverse as supported metalcatalysts. The book does not aim to do this, but
presents each chapter in a readable manner, withoverviews of the critical aspects of the subject anda thorough reference list for the reader to findgreater detail if they wish. As a stand-alone publi-cation, it provides good reference to aspects ofheterogeneous catalysis. As part of the “CatalyticScience Series”, it is an invaluable tool to researchstudents and industrial chemists in catalysis.
The Reviewer
Neil McGuire is a Senior DevelopmentChemist (Catalyst and ChiralTechnologies) at Johnson MattheyCatalysts in the U.K. His main interestsare platinum group metalheterogeneous catalysts for use in thepharmaceutical, fine chemical andagrochemical industries.
It is well known that for noble metal particlessupported on certain oxides, catalytic activity andselectivity for certain reactions such as CO hydro-genation can be strongly enhanced bypre-reduction. This results in the migration ofatoms from the support to the surface of the noblemetal particle itself to build up a partial monolayer,and is known as the strong metal-support interac-tion (SMSI) effect. However, in general it has alwaysbeen thought that some exposed metal surfaceatoms are necessary to allow chemisorption andsubsequent reaction.
Now, for the first time, we have shown that thecomplete encapsulation of noble metal particles bya reactive support also leads to good activity andexcellent selectivity for the water gas shift (WGS)reaction (1).
Using solution microemulsion techniques wehave made CeO2-encapsulated platinum (Pt) andPt/Au (platinum/gold) particles and tested theirWGS activity against Pt/CeO2 catalysts made inmore conventional ways. In contrast to the conven-tional catalysts, very few exposed Pt surface siteswere found when CO was used as a probe to detectany surface Pt. On testing the catalyst using a typi-cal WGS feed, better activity was found than withconventional catalysts, and more importantly therewas no evidence of the competing reaction ofmethanation. This provides the strongest evidenceof effective encapsulation of the Pt particles.
Characterisation of the encapsulated particles byUV spectroscopy showed a correlation of activitywith CeO2 electronic structure suggesting that thepresence of Pt enhances the ability of CeO2 toundertake redox chemistry and hence becomeactive for the WGS reaction. Therefore, the encap-sulation of noble metal particles by reactive oxidecoatings such as CeO2 represents a new class of cat-alytic material which has the ability to be tuned toachieve good activity and selectivity.
Reference1 C. M. Y. Yeung, K. M. K. Yu, Q. J. Fu, D.
Thompsett, M. I. Petch and S. C. Tsang, J. Am.Chem. Soc., 2005, 127, (51), 18010
Effects of Completely Encapsulating Platinum in Ceria
The Authors
S. C. Edman Tsang is Professor ofNanomaterials and Catalysis at theUniversity of Reading, U.K. He is interestedin fundamental and applied aspects ofnovel nanosize materials as heterogeneouscatalysts, solid state absorbents andsensors, which includes synthesis, testingand characterisation of these materials. E-mail: [email protected]
David Thompsett is a Scientific Consultantresponsible for the Electrotechnology &Catalyst Preparation Department at theJohnson Matthey Technology Centre, U.K. Hisinterests include fuel cells, catalystpreparation and characterisation, and therelationship between catalyst activity andstructure. E-mail: [email protected]
DOI: 10.1595/147106706X95356
22Platinum Metals Rev., 2006, 50, (1), 22–26
The 7th European Congress on Catalysis(EUROPACAT-VII – A Key to a Richer andCleaner Society), organised by the BulgarianCatalysis Club and the Greek Catalysis Societyunder the auspices of the European Federation ofCatalysis Societies (EFCATS) took place in Sophia,Bulgaria, from the 28th August to 1st September,2005. In all there were 773 registered delegatesfrom 39 countries and 750 presentations – 170 oraland 580 posters. At the end of each oral session,selected posters were described in two-minuteflash oral presentations, and 200 posters were cov-ered in this way. The oral presentations weregrouped into 11 different symposia covering mostareas of heterogeneous catalysis from fundamentalcatalysis and surface science to industrial catalysis.
Several symposia featured work on the plat-inum group metals, and the papers reported hereare grouped into very general categories.
EFCATS Sponsored AwardsTwo awards are made at this Congress. One is
the Johnson Matthey Award for Innovation inCatalysis, which was awarded to ProfessorValentin N. Parmon of the Boreskov Institute ofCatalysis, Novosibirsk, Russia. The other award isthe François Gault Lectureship, and ProfessorGraham Hutchings of Cardiff University, U.K.became the award holder for 2006. The holder ofthis position acts as an ambassador for catalysis bylecturing around Europe.
Catalyst PreparationA one-step flame synthesis route to
Pt/Ba/Al2O3 was described by Reto Strobel (ETHZurich, Switzerland). The material was preparedusing two flame spray pyrolysis nozzles, one forthe Al precursor and the other for the Pt/Ba pre-cursors. The resulting material was found to have
good NOx storage capacity. However, materialmade with only one nozzle for the Pt, Ba and Alhad no NOx storage capacity.
Plasma spraying and cold gas dynamic spraymethods used in preparing palladium (Pd), Pd-Mn,Cu-Cr and Mn catalysts for methane combustionwere described by O. Yu. Podyacheva and cowork-ers (Boreskov Institute of Catalysis), and O. P.Solonenko and V. F. Kosarev (Institute ofTheoretical and Applied Mechanics, Novosibirsk,Russia). The cold gas method was employed todeposit the metals onto thin metal foils, althoughother types of support, such as sheet, metal plateand foam were also discussed. In the procedure, alayer of alumina was deposited onto the metal sur-face for good adhesion, this was followed by asecond alumina phase, and then the catalyst.Samples were characterised by XRD, SEM andXPS. SEM and thermal testing confirmed excellentadhesion and thermal stability. It was suggestedthat the samples could be suitable for use in thecatalytic chambers of gas turbines.
The design of a Pd/carbon coated asymmetricα-Al2O3 membrane catalyst for the production ofhydrogen peroxide (H2O2) by direct syn-thesis was described by S. Melada andcolleagues (University of Venezia, Italy)and G. Centi (University of Messina,Italy). The procedure involved coating analumina tube with a ceramic layer then a carbonlayer, followed by Pd deposition. The effect of thePd oxidation state, H2 partial pressure and synthe-sis variables were discussed. Results indicated thatboth a high partial pressure of hydrogen and sur-face oxidised Pd particles were needed for highactivity. H2O2 is extensively used in the pulppaper/textile industries and is currently producedby the anthraquinone process. This process is notideal, but other methods of production need to
DOI: 10.1595/147106705X90154
7th European Congress on CatalysisACADEMIC AND INDUSTRIAL ADVANCES ON ALL FRONTS IN PGM HETEROGENEOUS CATALYSIS
By Stephen Poulston*, Andrew Smith** and Thomas Ilkenhans***Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.;
consider that potentially explosive mixtures can begenerated on scale-up. As the demand for H2O2 islikely to increase in the future (2M tonnes produc-tion in 2003), alternative production routes arecertainly of commercial interest.
Catalyst CharacterisationProfessor M. Neurock (University of Virginia,
U.S.A.) gave a plenary lecture entitled ‘First-princi-ples elucidation and design of catalytic sites andtheir environments’. He discussed the necessity forunderstanding, on an atomic scale, the active sitesthat control catalytic behaviour and their localreaction environment, as both are important in thesearch for more active and selective catalysts.Defect surface sites, bimetallic alloys, promoters,poisons, coadsorbed intermediates and the catalystsupport can all change the nature of the adsor-bate/surface interactions. Professor Neurock usedab initio quantum mechanical methods and theoryto study alloys for catalytic and electrocatalytic sys-tems, including lean NOx catalysis.
Professor R. Schlogl (Fritz Haber Institute,Berlin, Germany) emphasised the need for bothstatic and dynamic characterisation of catalysts to
improve functional understanding of catalytic sys-tems. One example used to illustrate this was theselective hydrogenation of pentyne over a range ofPd surfaces: single crystal Pd(111), Pd foil andPd/alumina. High resolution XPS identified thepresence of surface, sub-surface and bulk dis-solved carbon.
Microscopy with ‘SuperSTEM’ (scanning trans-mission electron microscope) was described by J.L. Casci (Johnson Matthey Catalysts, Billingham,U.K.) for characterising promoters in cobaltFisher-Tropsch catalysts. The technique is capableof sub-Ångstrom resolution, and was used to findthe location of promoter atoms in the Co/aluminacatalyst. Catalyst samples, prepared by the cobaltammine carbonate deposition-precipitationmethod, were post-impregnated with Pt, Ir, Re orRu precursors. A high-angle annular dark-fielddetector produced atomic number contrast imag-ing, while electron energy-loss spectroscopy(EELS) was used for elemental spectroscopy. ThePt, Ir and Re promoters were mainly present asisolated atoms, while the Ru promoter was presentboth as isolated atoms and in regions of high con-centration with Co particles. All four elements
Platinum Metals Rev., 2006, 50, (1) 23
The Johnson Matthey Award for Innovation in CatalysisThe Johnson Matthey sponsored
“Innovation in Catalysis” award has beenpresented now at three EUROPACATmeetings. At EUROPACAT-VII, ProfessorValentin Parmon of the Boreskov Instituteof Catalysis, Novosibirsk, Russia, was grantedthe award for “his fundamental contributionto the development of catalytic andphotocatalytic solutions to sustainableprocesses and energy”. The award is managedand administered by the European Federationof Catalyst Societies.
At EUROPACAT-V the award wasconferred on Pierre Jacobs (KatholiekeUniversiteit Leuven, Belgium) and atEUROPACAT-VI on Giuseppe Bellussi(EniTecnologie, Italy).
Professor Valentin N. Parmon holding the award.On his left is the Chairman of EFCATS,Professor Gabriele Centi (University of Messina,Italy), and on his right is John L. Casci (JohnsonMatthey Catalysts) who presented the award
Platinum Metals Rev., 2006, 50, (1) 24
promoted the reduction to metallic cobalt, butonly Ru, Pt and Ir were effective in lowering thetemperature of the Co3O4 to CoO transition. Lateranalysis, including in situ XRD, showed the reduc-tion of Co3O4 to CoO to Co metal.
R. N. Devi (Queen’s University of Belfast,U.K.) presented work on preparative aspects of a5% Pt-0.5% Fe catalyst coated with Na-A zeolitefor the selective oxidation of CO in the presenceof n-butane. The zeolite coating allows the CO toreach the Pt catalyst but inhibits the n-butane. Thisleads to a big difference in the catalyst light-offtemperature.
Theoretical Methods andFundamental Studies
Professor R. Burch (Queen’s University Belfast,U.K.) stressed, as did many presenters, the needfor in situ characterisation to identify reactionmechanisms. Steady state isotopic transient kinetic(SSITK) measurements were combined with dif-fuse reflectance infrared Fourier transformspectroscopy (DRIFTS) to look at the forward andreverse water gas shift reaction over Pt/CeO2. TheDRIFTS equipment was designed to minimise res-idence time, in order to give a time resolution of afew seconds, and to prevent gas bypassing the cat-alyst to give improved kinetic data. The datashowed that the carbonyl and carbonate species onthe catalyst surface decayed at the same rate as thelabelled CO, but that formate decayed much moreslowly, indicating it was a minor intermediate inthe reaction pathway under the conditions used.
C. R. Henry (CRMCN-CNRS, Marseille,France) described a surface science approach forproducing a model supported catalyst. A Ni3Al(111) single crystal was oxidised at 1000 K to givean alumina film surface with a regular array ofdefects. Pd was deposited, and then gold (Au), andthe bimetallic particles gave an ordered array ofclusters. The spatial distribution of the Au and Pdis controlled by the surface defects.
metals-promoted titania systems for hydrogenproduction. The first talk, by M. Kitano (Kansai
University, Japan), described a visible light-respon-sive Pt/TiO2 thin film photocatalyst produced bymagnetron sputtering of Pt onto a planar TiO2
substrate. This configuration allowed the Pt andTiO2 sides of the catalyst to be physically separate,to prevent recombination of the O2 (produced onthe TiO2) and the H2 (produced on the Pt), andthus easy separation of the two gases. The titaniawas a mixture of rutile and anatase, and the coat-ing procedure produced TiO2 slightly reduced atthe surface. The TiO2 was sensitive to visible light.
The second talk, by Professor M. J. Bowker(University of Cardiff, U.K.) described a Pd/TiO2
(P25) photocatalyst for reforming methanol to H2
and CO2 using UV light. The Pd loading had astrong influence on activity, which reached a max-imum at 0.5 wt.% Pd.
The photocatalysed degradation of pesticidesand organic pollutants was discussed by D.Bahnemann (University of Hanover, Germany),and M. Muneer and colleagues (Aligarh MuslimUniversity, India). They examined thedegradation of pesticide derivatives,such as N,N-dimethyl-α-phenyl ben-zene acetamide (diphenamid), bromacil,terbacil and 2,4,5-tribromoimidazole(TBI), and other pollutants, such as ben-zidine. Aqueous suspensions of TiO2
were investigated under varying conditions of pH,substrate, photocatalyst concentration, type ofTiO2 and the presence of H2O2 as an alternativeadditive to O2. Several factors were found to beimportant for electron transfer and it was specu-lated that in order to improve the electronic effectsin the reaction, mixed semiconductors(TiO2/SnO2) and Pt, Pd, Au or Ag might have tobe included.
Catalyst Deactivation as Part ofCatalyst Design
Professor S. D. Jackson (University ofGlasgow, U.K.) highlighted the role of catalystdeactivation as a key part of catalyst design.Examples of catalyst deactivation in industrialprocesses were given, including propane dehydro-genation for which Pt and Cr catalysts werecompared. Both catalysts deactivate quite rapidly,
Pt in 3 to 5 days, and Cr in 15 to 25 minutes.Processes have been designed to manage this deac-tivation, for instance, the Oleflex process (propaneto propylene) from UOP using a Pt catalyst, andthe Catofin® process from Houdry, using a Cr-based catalyst.
Fine Chemical SynthesisTwo presentations examined the use of pre-
cious metal catalysts for the synthesis of finechemicals and their intermediates.
H. Markus and colleagues (Åbo AkademiUniversity, Turku, Finland) discussed the use of Pdsupported on zeolites for the hydrogenolysis of thelignan hydroxymatairesinol to matairesinol
(matairesinol is an anticarcinogenic andantioxidative lignan). The work describedthe extraction of hydroxylmatairesinolfrom Norway spruce (Picea abies) knots,
which in 1998 were found to contain up to 10%lignans, with hydroxymatairesinol being the mostabundant. The synthesis was carried out in a stirredglass reactor under hydrogen flow with 2-propanolas the solvent. Several Pd/zeolite catalysts wereinvestigated and characterised by metal dispersion,surface area, support acidity, pore size and metalcontent. A bifunctional mechanism for thehydrogenolysis was proposed, requiring both metaland acid sites. Relatively large pores in the zeolitewere considered important to allow the bulky reac-tant molecules access to the active sites. Theresults indicated that the reaction rate was inverse-ly dependent on the acidity of the supportingzeolite.
E. Sulman and coworkers (Tver TechnicalUniversity, Russia), P. Valetsky and colleagues(Nesmayanov Institute of Organoelement
Compounds, Moscow, Russia), and P.Valetsky and L. Bronstein (IndianaUniversity, U.S.A.) discussed the synthe-sis of vitamin intermediates and fragrantsubstances by metal-polymeric nanocata-
lysts. They looked at the use of stabilised preciousmetal nanoparticles for achieving high selectivity,activity and technological performance. Differenttypes of metal-polymeric catalysts, in Pd, PdZnand PdPt systems, were reviewed and the impor-
tance of the stabiliser towards activity was empha-sised. They claimed improved activity and goodselectivity, compared to a commercially availablePd catalyst.
Environmental CatalysisProfessor R. Prins (ETH Zurich, Switzerland)
gave a plenary lecture on ‘Hydrotreating catalysis: acontribution to cleaner air!’. He discussed hydro-desulfurisation (HDS) and hydrodearomatisation(HDA) over pgm/alumina catalysts. Although sys-tems based on MoS2 are the main candidates forHDS catalysts, pgm-based catalysts may be usefulto further reduce the sulfur levels in a secondarysulfur removal step. At 300ºC and 50 atm the orderof catalyst activity for the hydrogenation of diben-zothiophene (to produce mostly biphenyl) wasfound to be: Pd-Pt alloy > Pt > Pd. When themore sterically hindered 4,6-dimethyldibenzothio-phene underwent HDS, Pd gave a betterperformance than Pt, and Pd also produced muchstronger hydrogenation, in this case giving pre-dominantly 3,3-dimethylbicyclohexyl.
Work on a reformer for producing hydrogenfrom dimethyl ether was described by L. J.Pettersson (KTH-Royal Institute of Technology,Stockholm, Sweden). The hydrogen could then beused for catalyst regeneration (such as in a NOxtrap) and to feed PEM fuel cells acting as auxiliarypower units. The latter could, for example, providepower to run air conditioning at idle.
The leaching of nitrates from soil into watersupplies is known to be due to excessive use ofnitrate-based fertilisers in agriculture. In1998 the European EnvironmentalAgency estimated that 87% of the agri-cultural land in the EU has nitrateconcentrations above the guide level of25 ppm. The EU has set an upper level of50 ppm as the maximum permitted concentrationof nitrates in drinking water, and amounts abovethis are deemed unacceptable. One method ofnitrate removal is to convert the nitrate ions intonitrogen. This can be achieved by liquid phasenitrate hydrogenation over, generally, heteroge-neous bimetallic catalysts. However, more recentwork has looked at monometallic catalysts with a
nitratesleach intogroundwater
matairesinolproduction
synthesis ofvitaminintermediates
semiconducting support, such as TiO2. Professor J.A. Anderson (Aberdeen University, U.K.) present-ed work aimed at developing procedures toimprove understanding of the catalyst under work-ing conditions. He gave results of in situ FTIR andXAS examination of Pd/TiO2 catalyst used tohydrogenate nitrates in aqueous solution. ThePd/TiO2 catalyst was prepared from TiO2 P25(Degussa) and a Pd precursor (Johnson Matthey).His results suggested that the catalyst convertsnitrates to N2 without forming the nitrite.However, the selectivity was considered inade-quate.
Work on hydrogenation and oxidation reactionson core-shell nanoparticles of Pd-Ni/MgO waspresented by S. Sao Joao and colleagues (CRMCN-CNRS, France), and L. Piccolo and C. R. Henry(IRC-2, France). Generally, the deposition of a thinlayer of metal A onto a bulk metal B is know toalter the valence band of bulk B due to coordina-tion, the lattice strain of metal A and the nature ofthe metals. In this work, a Ni core was prepared onMgO, and Pd was deposited onto the surface bybubbling hydrogen through the precursors (Pdacetylacetonate and Ni/MgO) in toluene. TEManalysis showed the core-shell structure of a Pdshell around the Ni core. The materials were testedfor butadiene hydrogenation and CO oxidation.
Electrochemical PromotionSeveral presentations focused on the phenome-
non of electrochemical promotion (EP), alsoknown as NEMCA (non-Faradaic electrochemicalmodification of catalytic activity). This relies on theapplication of a potential across an ionic conductorto alter its surface composition. The conductorcarries a deposited catalytic metal, and the alteredcomposition affects the activity of the catalyst.Professor Richard Lambert (Cambridge University,U.K.) illustrated the EP effect with a substrate ofion conducting β''-alumina, where Na or K ispumped to and from the surface on application ofpotential. Several applications were discussed,including a Fischer-Tropsch reaction over Rh coat-ed K-β''-alumina. The K promotion led to anincrease in ethanol production. Recent work wasalso described on using Pt coated Na-β''-alumina
Stephen Poulston is aPrincipal Scientist at theJohnson MattheyTechnology Centre(JMTC), SonningCommon, U.K. He worksin the Gas PhaseCatalysis Group. Hismain interests lie inheterogeneous catalysts.
Dr Andrew W. J. Smith isa Senior Scientist in theGas Phase CatalysisGroup at JMTC. He is asynthetic inorganicchemist with experienceof materials and catalystpreparation. He isinterested in developingnew materials and theirapplications inheterogeneous catalysis.
Thomas Ilkenhans is aResearch Chemist in theGas Phase CatalysisGroup at JMTC. He isinterested in usingpalladium in catalysis.
The Reviewersas a NOx storage device(analogous to those usedin automotive applicationsfor NOx removal in leanburn engines) where thenitrate can be decomposedby pumping Na away fromPt on application of volt-age.
A breakthrough in thepractical applications forEP was presented byProfessor Costas Vayenas(University of Patras,Greece) who described amonolith-type reactor con-sisting of 22 parallel platesof YSZ coated on one sidewith Pt and on the otherwith Rh. This would allowfor the processing of largevolumes of gas withoutsignificant bypass issues, ina compact device.
ConclusionThe vitality, breadth,
and success in researchand development in het-erogeneous catalysis withthe platinum group metalswas well demonstrated atthis congress.
The next congress,EUROPACAT-VIII, enti-tled ‘From Theory toIndustrial Practice’ will beheld from 26th to 31stAugust 2007, in Finland atTurku/Åbo. It will be runby the Nordic CatalysisSociety, and will be a jointeffort by Denmark,Finland, Norway andSweden. More informationcan be found from:http://www.europacat.org/
26Platinum Metals Rev., 2006, 50, (1)
27
Patents are a key source of technical and com-mercial intelligence, as described in a previousarticle in this Journal (1). Osmium is often seen asthe forgotten member of the platinum group met-als, but nevertheless still attracts interest (2, 3).
Modern software allows us not only to searchout patents relating to osmium, but also to visu-alise the search results. The landscapes, (Figures 1and 2) were created using the AurekaThemeScapeTM software (4) which uses statisticalalgorithms to analyse the usage of words andphrases, and discern themes and relationshipsamong documents. They show the results of apatent search on osmium covering the period 1981
to 2005 in the US (United States), EP (EuropeanPatent), PCT (Patent Cooperation Treaty), GB(British) and JP (Japanese) patent collections.Figure 1 shows a ThemeScape map of the set of3400 patent documents in which the word osmiumappears in either the title, the abstract or theclaims, once duplicate family members have beenremoved. The map labels represent key themeswithin particular sections of the map. Figure 1clearly depicts clusters of patents relating to cataly-sis (e.g. “acid, acetic acid, carbonylation”;“metathesis, alkyl, ligand”), fuel cells and sensors(e.g. “electrode, reference, sensor”, “anode, cath-ode, electrolyte”), and electronic applications (e.g.
Platinum Metals Rev., 2006, 50, (1), 27–28
DOI: 10.1595/147106706X91404
Osmium – The Patent LandscapeA VISUALISATION OF THE TECHNOLOGY DESCRIBED IN PATENTS RELATING TO OSMIUM
By Richard SeymourJohnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, U.K.; E-mail: [email protected]
Fig. 1 A patent landscape based on ~ 3400 patents in which osmium is mentioned in the title, abstract or claims
“capacitor, layer, device”, “layer, electrolumines-cent, device”). The search could be narrowed todisplay patents in which osmium occurs only in thetitle or abstract (just over 800 patents), or bebroadened to show patents in which osmiumappears in the full patent specification (> 14,000patents).
In Figure 1, the dots in the map are examples ofspecific patents. Clicking on a contour will pick upall the patents within that contour line, which isuseful when further analysis of an area is required.The blue “ocean” represents areas of low patentactivity.
It is possible to use to use this map to identifytrends in patent activity over time, or to illustratethe patent activity of a particular company (bymeans of coloured dots). For example, Figure 2shows patenting by three companies selected atrandom: red, a pharmaceuticals company; green, achemicals company; yellow, an electronics compa-
ny. With this patent visualisation approach, abroad picture of the actual and potential uses ofosmium can be obtained, and be followed by moredetailed examination of clusters of specific interest.
References1 I. Wishart, Platinum Metals Rev., 2005, 49, (2), 982 J. W. Arblaster, Platinum Metals Rev., 2005, 49, (4),
The AuthorRichard Seymour is the Head ofTechnology Forecasting andInformation at the Johnson MattheyTechnology Centre in the U.K. He isinterested in the use of information inthe areas of competitive intelligence,technical innovation and new productdevelopment.
Platinum Metals Rev., 2006, 50, (1), 27–28 28
Fig. 2 The osmium patent landscape showing the patent filing activity of a pharmaceuticals company (red), achemicals company (green) and an electronics company (yellow)
Platinum Metals Rev., 2006, 50, (1), 29–34 29
Iridium (Ir) is a noble metal with the highestmelting point, 2719 K, of all the face centred cubicmetals (1). It is a secondary fixed point on theInternational Temperature Scale (ITS-90) (2), andis used as a high-temperature and heat-resistantconstruction material (3–5). The working tempera-ture of Ir is from ~ 1300 to 1800 K, ~ 0.48 to ~0.67 Tm (Tm is the melting point of Ir). Over thistemperature range, Ir crucibles are used in theextraction of gold (Au) from zinc scrap. At thesetemperatures, the ‘impurity’ mechanism of volumediffusion in metals can be seen more clearly, andthe diffusion of impurities (in this case Au throughIr) has been found to be many orders of magnitudehigher than estimates made by measuring the coef-ficients of volume self-diffusion in Ir (6).
Prior WorkTheoretical and experimental studies of the
atomic mechanisms of diffusion and of typical fea-tures of volume diffusion indicate that atomicmechanisms are an efficient tool for analysingmicroscopic interactions between point defects(vacancies and impurities) participating in diffu-sion. The parameters of volume diffusion in solidsare determined by mutual interactions betweensuch point defects (6–13).
The effect of substitutional and interstitialimpurities on the diffusion parameters of atomsused as atomic probes in metals has previouslybeen studied (13–19). Work has also been done onthe thermodynamics of formation of vacancy-impurity complexes (VICs) in interstitial solid
DOI: 10.1595/147106705X84412
Mechanisms of Volume Diffusion of Goldinto Single Crystal IridiumEVIDENCE THAT VOLUME DIFFUSION, INTRINSIC OR EXTRINSIC, DEPENDS ON THE ATMOSPHERICCOMPOSITION WHICH OCCURS DURING ANNEALING OF SINGLE CRYSTAL IRIDIUM
By S. M. Klotsman*, S. A. Matveev, G. N. Tatarinova, A. N. TimofeevLaboratory of Diffusion, Institute of Metal Physics, Ural Branch RAS, 620219 Ekaterinburg, Russian Federation;
and A. V. Yermakov and V. K. RudenkoEkaterinburg Non-Ferrous Metals Processing Plant JSC, Ekaterinburg, Russian Federation
Iridium crucibles, examined after being used in the extraction of gold and silver from residuesremaining after zinc manufacture, showed an anomalously high permeability to substitutionalcomponents and impurities, such as gold. To discover the cause of this high permeability,the volume diffusion of gold into nominally pure single crystals of iridium (single-Ir), annealedunder ultrahigh and technical grade vacuums, UHV and TGV, respectively, was studied attemperatures from 1300 to 2000 K. The coefficients of volume diffusion of gold into single-Ir were measured by secondary ion mass spectrometry. The activation enthalpies measuredfor volume diffusion of the gold were: (Q Au
Ir )UHV = (423 ± 5) kJ mol –1 and (Q AuIr )TGV = (193 ±
27) kJ mol –1 in UHV and TGV, respectively, for annealing single-Ir. On annealing in TGV,interstitial impurities formed vacancy-impurity complexes (VICs). The binding energy of theVIC components (EVIC)Ir = (116 ± 16) kJ mol –1. In TGV, the gold diffusion was determinedby ‘extrinsic’ vacancies dissociating from the VICs. At typical working temperatures for iridiumthe concentration of the ‘extrinsic’ vacancies was several thousand times larger than theconcentration of the equilibrium ‘intrinsic’ vacancies. The ‘extrinsic’ vacancies are responsiblefor the high coefficient of volume diffusion and the corresponding anomalously high masstransfer of gold into iridium during TGV annealing.
solutions, and thermodynamics has been used todescribe the diffusion of substitutional atomicprobes in interstitial solid solutions of carbon iniron (C(Fe)) and carbon in palladium (C(Pd))(15–18).
The formation of a VIC flow during carbon dif-fusion in platinum has been vividly demonstrated(18, 19). Pores formed in the diffusion zone, wherecarbon had diffused into the platinum, due to thecondensation of ‘extrinsic’ vacancies released dur-ing thermal dissociation of the VICs. The bindingenergy of the VIC components in the platinum is:|EVIC| > 50 kJ mol–1.
This paper presents results of a study of the vol-ume diffusion of Au into single crystals of Ir(single-Ir) of 4N (99.99%) purity during annealingin an ultrahigh vacuum (UHV) and a technicalgrade vacuum (TGV). The single-Ir crystals weregrown at the Ekaterinburg Non-Ferrous MetalsProcessing Plant. Single crystals do not have grainboundaries. Coefficients of volume diffusion in
TGV, (DAuIr )TGV, were measured in single-Ir
annealed in a TGV at the working temperatures ofIr. The values obtained were several thousandtimes larger than coefficients of volume diffusion,(DAu
Ir )UHV, measured for the same samples in UHV.This is due to a new diffusion mechanism foundduring annealing in TGV. The mechanisminvolves ‘extrinsic’ vacancies which arise from dis-sociation of the VICs.
Theoretical BackgroundThe profile of diffusing species (the diffusant)
within a homogeneous sample is described byExpression (i) (6):
C(y,t) = C0(t) exp(– y2/4Dt) (i)
where C(y,t) is the concentration of the diffusant(in this case gold) at depth y in the sample, andC0(t) is the concentration at the surface where y =0; t is the diffusion annealing time, and D is thecoefficient of volume diffusion. D is determined
Platinum Metals Rev., 2006, 50, (1) 30
Fig. 1 Straightened gold profiles in single-Ir annealed inTGV and measured by secondary ion mass spectrometry(SIMS) using primary O+ and Cs+ beams. The straightlines were drawn using the least squares method. Thedepth scales of the given profiles were extended byapplying the following coefficients: (1) × 85; (2) × 50;(3) × 20; (4) × 1
Fig. 2 Straightened gold profiles produced in single-Irannealed in UHV and measured by the SIMS methodusing primary O+ and Cs+ beams. The straight lines weredrawn using the least squares method. The depth scalesof the profiles: 1, 2, 3 and 4, were extended by applyingthe following coefficients to them: (1) × 85; (2) × 50; (3) × 20; (4) × 1
1.0 x 10–10 2.0 x 10–10
(DEPTH)2, m2
5.0 x 10–12 1.0 x 10–11
(DEPTH)2, m2
101
100
10–1
10–2
10–3
104
103
102
101
10–0
10–1
10–2
10–3
I – I t
ail,
rel.
units
I – I t
ail,
rel.
units
Au(Ir)TGV Au(Ir)UHV
from the slope of the linear function in (ii):
ln C = –y2/4Dt (ii)
The activation enthalpy, Q, for volume diffusion isgiven by the relationship (iii):
ln D = –Q/RT (iii)
where R is the gas constant and T is the annealingtemperature.
The interaction energy (binding energy) EVIC, ofthe components in the VICs is determined fromExpression (iv) (12–14):
EVIC = [ QVIC – Q ] (iv)
2
where QVIC is the activation enthalpy for diffusionby ‘extrinsic’ vacancies dissociating from VICs.
ResultsGold Profiles in Single-Ir after Annealing inUHV or TGV
The volume diffusion of Au in Ir was studiedusing single-Ir. The materials, their preparationand measurement by secondary ion mass spec-trometry (SIMS) are described elsewhere (20, 21).The dependence of ln IAu(y2 ), where IAu is theintensity of secondary Au ions, recorded duringSIMS analysis of single-Ir annealed in TGV orUHV, and y2 is the square of the depth (y) in theIr, is shown in Figures 1 and 2 (see Expressions (i)and (ii)). The same samples were annealed alter-
nately in UHV or TGV in a random sequence ofannealing temperatures.
The profiles of all the measured diffusion zoneswere characteristic of volume diffusion (7), that is,the dependencies, ln IAu(y2 ), were linear over abroad range of concentrations and remained linearup to the initial surface of the samples. In all cubiccrystals the crystal orientation is not important fordiffusion (6).
Temperature Effects of Diffusion Coefficientsin Single-Ir Annealed in UHV or TGV
Diffusion in solids follows the Arrhenius equa-tion, and the Arrhenius dependence of thecoefficients of volume diffusion for Au in Ir, (DAu
Ir )UHV and (DAuIr )TGV, are shown in Figure 3. At
low temperatures (1/T > 0.75) it can be seen thatcoefficients (DAu
Ir )TGV are 3 to 4 orders of magni-tude larger than coefficients (DAu
Ir )UHV. Theparameters D0 and Q of the Arrhenius dependen-cies of the coefficients of self diffusion, DSD, (3),and the coefficients of volume diffusion (DAu
Ir )UHV
and (DAuIr )TGV are given in Table I.
DiscussionMechanism of Gold Diffusion in Single-Irduring Annealing in UHV and TGV
The activation enthalpy for self diffusion, QSD,(22) and the activation enthalpy for volume diffu-sion (QAu
Ir )UHV of Au in single-Ir under UHVconditions (see Table I) are related as Expression (v):
Platinum Metals Rev., 2006, 50, (1) 31
Table I
Values for Parameters: D0 and Q of the Arrhenius Dependencies of Self Diffusion (7) and VolumeDiffusion of Gold in Single Crystals of Iridium, and for the Binding Energy EVIC between VIC Partners
System 192Ir (single-Ir) Au (single-Ir)UHV Au (single-Ir)TGV
Reference (22) (This work)
Temperature, K 2020–2600 1300–2000 1300–2000(0.74–0.96)Tm (0.48–0.73)Tm (0.48–0.73)Tm
D0, m2 s–1 3.5 × 10–5 5.4 × 10–5 1.7 × 10–10
Q, kJ mol–1 449.5 ± 0.3 424.3 ± 5.2 193 ± 27
QAu/QIr 0.94 0.43
EVIC, kJ mol–1 –(231 ± 32)
(QAuIr )UHV/QSD = 0.94 (v)
Expression (v) is characteristic of the volumediffusion of substitutional impurities assisted byequilibrium, ‘intrinsic’ vacancies in pure metals (6).The ‘intrinsic’ vacancies arise from thermal effects.However, for annealing Ir in a TGV we obtained:
(QAuIr )TGV/QSD = 0.43 (vi)
It follows from Expressions (v) and (vi) thatvolume diffusion occurs by ‘extrinsic’ vacanciesrather than by equilibrium ‘intrinsic’ vacancies dur-ing TGV annealing at temperatures below 2000 K(~ 0.73 Tm). Using Expression (iv) and the mea-sured activation enthalpies for Au diffusion, thebinding energy, EVIC, of the interaction betweenthe components in the VICs can be determinedfrom Expression (iv):
EVIC = 0.5[(QAuIr )TGV – (QAu
Ir )UHV]
= 0.5[(193 ± 27) – (424 ± 5)]
= – (116 ± 16) kJ mol–1 (vii)
The negative value indicates that stable VICs areformed during TGV annealing. The large value of|EVIC| is important for determining the stability ofpoint defect complexes. Stable VICs form in Irduring TGV annealing when T < 0.73 Tm.
Concentration of InterstitialImpurities and Excess Vacancies
Excess vacancies are induced by interstitialimpurities in single-Ir during TGV annealing. Theconcentration, Cinterst, of the interstitial impuritieswhich form VICs in single-Ir during TGV anneal-ing is determined from the relationship ofpre-exponential factors, D0, in the Arrheniusdependencies of the corresponding diffusion coef-ficients:
This concentration of interstitial impurities thatform VICs in single-Ir, Cinterst ≅ (1–10) × 10–6 at.parts, is natural. The coefficients (Di) of diffusionDUHV and DTGV of gold in Ir are related to the con-centrations CVac,i of intrinsic or extrinsic types ofvacancies and their diffusion coefficients DVac (6):
Di = DVac × CVac,i (ix)
Di represents the gold diffusion coefficient ineither UHV or TGV, DVac is the diffusion coeffi-cient of vacancies which is the same for both Di. Itfollows from (ix) that the concentration (CVac)VIC ≡(CVac)extr of ‘extrinsic’ vacancies formed in TGVannealing is related to the concentration of equilib-rium vacancies CVac ≡ (CVac)intr formed in UHVannealing at each annealing temperature by therelationship between the corresponding diffusioncoefficients DTVG and DUHV, respectively. Forexample, at the annealing temperature of 1300 K:
{(CVac)extr /(CVac)intr}1300 K = {DTGV/DUHV}1300 K
≅ 2 × 10–18/4 × 10–22 = 5 × 103 (x)
Effects of VIC Participation in MassTransfer of Impurities in Iridium
The industrial use of Ir for crucibles andsheathings that are heated in air at temperaturesfrom 1300 to 1800 K, leads to the Ir being loaded
Platinum Metals Rev., 2006, 50, (1) 32
Fig. 3 Arrhenius dependencies of the coefficients ofdiffusion, D Au
Ir,in single-Ir annealed under UHV (O) andTGV (∆ ) conditions. The straight lines were drawn usingthe least squares method
D, m
2s–1
0.5 0.6 0.7INVERSE TEMPERATURE, 1000/T, K–1
10–15
10–16
10–17
10–18
10–19
10–20
10–21
with interstitial impurities, such as carbon, oxygen,hydrogen and nitrogen, from the ambient atmos-phere or from the processed contents of thecrucibles. Under these conditions, alloying of theiridum which contains these interstitial impuritiescauses, besides Ir embrittlement, saturation of theIr volume with VICs and these, as described, sup-ply excess ‘extrinsic’ vacancies that dissociate fromthe VICs.
Consequently, all substitutional impuritiesbecome capable of diffusing from the body of theIr crucible through the walls. Their diffusion coef-ficients are several orders of magnitude higherthan the diffusion coefficients for the same impu-rities in VIC-free Ir, see Figure 3. This explains thehigh permeability of Ir walls to impurities such asgold. In addition, the accumulation of VICs andpores adjacent to internal interfaces, includinggrain boundaries, causes fast creep in the Ir sheath(3) and intercrystalline fracture, which appears as aspecific intercrystalline embrittlement (23).
In order to prevent the appearance and growthof VICs in Ir used at high temperatures in air, it isnecessary to alloy the Ir with components thathave a larger affinity for interstitial impurities thanIr, and form VICs with the impurities. Such VICsmust possess the highest binding energies, EVIC.
Typical components that will bind all interstitialimpurities (oxygen, carbon and nitrogen) arehafnium or thorium, etc. Their melting points andtheir binding energy with the interstitial impuritiesare much higher than those of Ir. With thismethod of preventing VIC formation, the lifetime
of products made from Ir-based alloy is deter-mined by the components of the complexesformed in the Ir.
When electrodes of Ir alloys containing severalweight percent of rhenium and ruthenium wereused to weld vessels made of Ir rolled stock, thepermeability of Au into Ir was considerably inhib-ited in walls near the weld seams. This resultconfirms our conclusion concerning the positiveoutlook for alloying Ir with elements that have alarger affinity for interstitial impurities than Ir.
ConclusionsThe activation enthalpy of volume diffusion of
Au in single crystals of Ir annealed in TGV isalmost half the value of the activation enthalpy ofthe volume diffusion of Au into single crystals ofIr annealed in UHV. This difference is explainedby the decisive contribution from ‘extrinsic’ vacan-cies that dissociate from the VICs, and is the causeof the large diffusivity of substitutional Au duringTGV annealing.
The large negative binding energy of the VICcomponents, –(116 ± 16) kJ mol–1, indicates thatVICs are formed by vacancies with interstitialimpurities (oxygen, hydrogen, nitrogen), thatalloyed with single-Ir during TGV diffusion.When products manufactured from Ir are heatedto high temperatures in air, Ir alloys are dopedwith the interstitial impurities, which form thebasis of the VICs and thus determine the ‘extrin-sic’ mechanism of the volume diffusion ofsubstitutional components in Ir.
Platinum Metals Rev., 2006, 50, (1) 33
References1 R. E. Bedford, G. Bonnier, H. Maas and F. Pavese,
http://www.bipm.fr/en/publications/its-90.html3 J. R. Handley, Platinum Metals Rev., 1986, 30, (1), 124 E. A. Franco-Ferreira, G. M. Goodwin, T. G.
George and G. H. Rinehart, Platinum Metals Rev.,1997, 41, (4), 154
5 N. I. Timofeev, A. V. Ermakov, V. A. Dmitriev andP. E. Panfilov, “The Base of Metallurgy andTechnology of Iridium Production”, Urals DivisionRAS, Ekaterinburg, 1996
6 H. Bakker, et al., in “Diffusion in Solid Metals andAlloys”, ed. H. Mehrer, Landolt-Börnstein, NewSeries, Springer Verlag, Berlin, 1990, Vol. III/26
7 S. M. Klotsman and A. N. Timofeev, Phys. Met.Metallogr., 1997, 83, (3), 86
8 S. M. Klotsman and A. N. Timofeev, Phys. Met.Metallogr., 1997, 83, (3), 295
9 S. M. Klotsman, S. A. Matveev, S. V. Osetrov and A.N. Timofeev, Phys. Metall. Metallogr., 1997, 83, (5),112
10 K. Richter, Zur Fremddiffusion von Übergangsmet-allen in Gold, Thesis, Technische UniversitätBergakademie, Freiberg, Germany, 1998
11 U. Klemradt, B. Drittler, T. Hoshino, R. Zeller andP. H. Dederichs, Phys. Rev. B., 1991, 43, (12), 9487
12 C. Köstler, F. Faupel and Th. Hehenkamp, Scr.Metall., 1986, 20, (12), 1755
Sergey A. Matveev, a SeniorResearcher at the DiffusionLaboratory, Department ofMetal Nanostructures, IMP,Ural Branch of the RAS. Hedeals with synthesis ofnonequilibrium metalnanostructures and analysisof their properties.
Alexander V. Yermakov, aSenior Researcher, Cand.Sc.(Phys. & Math.), is theDeputy Director of theEkaterinburg Non-FerrousMetals Processing Plant. Heis the author of monographsand over 150 scientificpublications and patents. Hisinterests lie in the study of theproperties and creation ofindustrial technology for theproduction of noble metalsand alloys.
Vladimir K. Rudenko is aPrincipal Research Engineer,Cand.Sc. (Phys. & Math.), inthe Research and EngineeringDepartment at theEkaterinburg Non-FerrousMetals Processing Plant. Heis the author of over 150scientific papers and patents.He is involved in the creationof materials based on thenoble metals, includingmaterials for hydrogen powerengineering, and investigates and analyses their properties.
13 J. Wolff, M. Franz, J.-E. Kluin and D. Schmid, ActaMater., 1998, 45, (11), 4759
14 R. B. McLellan, J. Phys. Chem. Solids, 1988, 49, (10),1213
15 R. B. McLellan, Acta Metall., 1988, 36, (8), 1923 16 N. Z. Carr and R. B. McLellan, Acta Mater., 2004, 52,
(11), 327317 C. Domain, C. S. Becquart and J. Foct, Phys. Rev. B,
2004, 69, (14), 14411218 K. Y. Westmacott, M. J. Witcomb and U. Dahmen,
Acta Metall., 1983, 31, (5), 75519 P. Ferguson, K. Y. Westmacott, R. M. Fisher and U.
Dahmen, Mater. Sci. Technol., 1985, 1, (1), 53
20 A. V. Yermakov, S. M. Klotsman, S. A. Matveev, G.N. Tatarinova, A. N. Timofeev, V. K. Rudenko andN. I. Timofeev, Phys. Met. Metallogr., 2001, 92, (2), 87
21 A. V. Yermakov, S. M. Klotsman, S. A. Matveev, G.N. Tatarinova, A. N. Timofeev, V. K. Rudenko, N.I. Timofeev and G. F. Kuzmenko, Phys. Metall.Metallogr., 2002, 93, (5), 45
22 N. K. Archipova, S. M. Klotsman, I. P. Polikarpova,A. N. Timofeev and O. P. Shepatkovskii, Phys. Met.Metallogr., 1986, 62, (6), 1181
23 A. Brookes, J. H. Greenwood and J. L. Routbort, J.Inst. Met., 1970, 98, (1), 27
Platinum Metals Rev., 2006, 50, (1) 34
Professor Semyon M.Klotsman, Dr.Sc. (Phys. &Math.), is the head of theteam at the DiffusionLaboratory, Department ofMetal Nanostructures,Institute of Metal Physics(IMP), Ural Branch of theRussian Academy of Sciences(RAS). He deals with studiesinto fundamental properties ofpoint (vacancies, impuritiesand their complexes) and
two-dimensional (internal interfaces, grain boundaries inpolycrystals) defects in solids. He is author of about 400scientific publications in leading international physicsjournals. http://www.imp.uran.ru/
Andrey N. Timofeev, SeniorResearcher, Cand.Sc. (Phys.& Math.), is a leadingresearcher at the DiffusionLaboratory, Department ofMetal Nanostructures, IMP,Ural Branch of the RAS. He isinterested in diffusionphenomena in metals anddielectrics. He is author ofabout 200 scientificpublications in internationalphysics journals.
Galina N. Tatarinova is aResearcher at the DiffusionLaboratory, Department ofMetal Nanostructures, IMP,Ural Branch of the RAS. Herscientific interests includeregular features of diffusion incondensed matter. She is theauthor of about 100 scientificpublications in leadinginternational physics journals.
The Authors
Platinum Metals Rev., 2006, 50, (1), 35–37 35
For creative, ingenious and skillful work in thefield of olefin metathesis and organometallicchemistry, the Nobel Prize for Chemistry in 2005was awarded to Yves Chauvin (Institut Français duPetrole), Robert H. Grubbs (California Institute ofTechnology) and Richard R. Schrock (MassachusettsInstitute of Technology) (1).
The metathesis of alkenes is a remarkable cat-alytic process in which, under the action of atransition metal compound, denoted by M, twoC=C double bonds in two alkene molecules arebroken and two new C=C bonds are sequentiallyformed (2), according to a metallocarbene/metal-lacyclobutane mechanism first formulated byChauvin (3). The two molecules may be identical(for example, two propene molecules afford ethyl-ene and E/Z-2-butene), or different (for example,R2C=CH2 and R′2C=CH2 yield ethylene andR2C=CR′2 ). In addition, an intramolecular ring-closing of a diene with two terminal double bonds,accompanied by the release of ethylene, has beendeveloped. The preferred catalysts are based on M= tungsten, rhenium, molybdenum, or rutheniumcompounds: with the last two types enjoying wide-spread applications in both organic and polymersynthesis, mainly due to extensive research bySchrock (4) and Grubbs (5). By varying sub-
stituents on the olefin substrate, a wide range offurther olefinic products become readily accessi-ble, while monocyclic or polycyclic olefins providepolymers with unprecedented structures and prop-erties (6).
First observed in the 1950s by H. S. Eleuterio(7), and subsequently by R. L. Banks, G. C. Bailey,W. E. Truett and others, the alkene metathesisreaction (a term coined by Calderon) and the relat-ed ring-opening metathesis polymerisation(ROMP) were developed in the following decadesby many scientists, each bringing remarkable con-tributions to this productive area of organicsynthesis and catalysis (8).
However, it was only in 1971 that a metal-car-bene intermediate was proposed by Y. Chauvinand his student J.-L. Hérisson, to explain – satis-factorily for the first time – the mechanism (3).This extraordinary mechanistic proposal, rational-ising Chauvin’s astonishing new observations, wasimmediately embraced by the metathesis commu-nity and prompted studies on metal-carbeneinitiators culminating in the creation of the molyb-denum-alkylidene catalysts by R. R. Schrock, seeFigure 1 (9), and the 1st and 2nd generation ofruthenium-alkylidene catalysts, by R. H. Grubbs,see Figure 2 (10).
DOI: 10.1595/147106706X94140
2005 Nobel Prize in ChemistryAWARDED FOR THE DEVELOPMENT OF THE METATHESIS REACTION IN ORGANIC SYNTHESIS
These transition metal alkylidene complexes, inthemselves a fine artwork in organometallic syn-thesis, allow extensive practical applications. Someare commercially available and used worldwide,applicable to large-scale or combinatorial synthe-ses. Full utilisation of these versatile catalysts is justbeginning, and by efficient and environmentally-friendly protocols they have opened many ways forobtaining a large variety of organic compoundsand natural products with intricate structures, rou-tinely used pharmaceutical intermediates,pesticides, polymers, and composite materials.
Remarkably, the above two types of metathesiscatalysts have their own merits and distinctive fea-tures thus broadening even more their areas ofapplication. For instance, Schrock’s molybdenum-based catalysts, Figure 1, display high activity andselectivity, while Grubbs’ ruthenium-based cata-lysts, Figure 2, are more tolerant to water andfunctionalities. With these catalysts, the promise of“green chemistry” in organic synthesis is dawning.
In addition to alkene metathesis and ROMPreactions, involving eight electrons (8e– ), relatedprocesses are now known (11). These formally
Acronyms of other reactions based on metathe-sis are: ADMET (acyclic diene metathesis), RCM(ring-closing metathesis), ARCM (asymmetric ring-closing metathesis) and ROM (ring-openingmetathesis).
Ruthenium has featured before in Nobel Prizework (13), and it plays a key role in building mod-ern metathesis catalysts. Reviews reflecting theoutpouring of rapid developments in ruthenium-based catalysis for metathesis have been and arebeing published in this Journal (14).
Lastly, over the past few years, metal-catalysedolefin metathesis has had an enormous impact onorganic synthesis, and is emerging as one of themost often used chemical transformations (15). Byawarding the 2005 Nobel Prize for Chemistry toChauvin, Grubbs and Schrock, the outstandingcontribution resulting from metathesis for theprogress of human society has now been rightfullyrecognised.
V. DRAGUTAN, I. DRAGUTAN AND A. T. BALABAN
Platinum Metals Rev., 2006, 50, (1) 36
Some prominent scientists who have worked on metathesis reactionsH. S. Eleuterio, R. L. Banks, G. C. Bailey, W. E. Truett, J. M. Basset, L. Bencze, C. Boelhouwer, M. R. Buchmeiser, N. Calderon, G. Natta, A. F. Noels, Y. Chauvin, A. Demonceau, P. H. Dixneuf, B. A. Dolgoplosk, J. M. Feast, E. Finkel’stein, A. Fürstner, R. H. Grubbs, W. A. Herrmann, K. Hummel, H. Hocker, Y. Imamoglu, K. J. Ivin, T. J. Katz, E. Khosravi, B. Marcinec, T. Masuda, J. C. Mol, A. Mortreux, S. P. Nolan, J. J. Rooney, R. R. Schrock, F. Stelzer, R. Streck, E. Thorn-Csanyi,F. Verpoort, K. Wagener, K. Weiss ..... and many others.
Me2HC CHMe2N
Mo MeMe
Ph
OO
MeF3C
F3C
CF3CF3Me
Fig 1. The Schrock catalyst
Ru
PR3
PR3
Cl
Cl
Ph
HRu
Cl
Cl
R'
R'
PR3
PR3
Ru
PR3
Cl
Cl
Ph
H
NNMes Mes
Ru
PR3
Cl
Cl
Ph
H
NNMes Mes
R is phenyl or cyclohexyl; Mes is mesityl
Fig. 2 (a) First ,(b) second generation Grubbs’ catalysts
(a)
(b)
1 (a) http://nobelprize.org/chemistry/laureates/2005/announcement.html; (b) A. M. Rouhi, Chem.Eng. News, Oct. 10, 2005, 83, (41), p. 8; (c) Angew.Chem. Int. Ed., 2005, 44, 6982
2 (a) N. Calderon, H. Y. Chen and K. W. Scott,Tetrahedron Lett., 1967, 8, 3327; (b) N. Calderon, E.A. Ofstead, J. P. Ward, W. A. Judy and K. W. Scott,J. Am. Chem. Soc., 1968, 90, 4133; the earliest bookson metathesis are: (c) V. Drãgutan, A. T. Balabanand M. Dimonie, “Metateza Olefinelor siPolimerizarea prin Deschidere de Inel aCicloolefinelor” (Rom.), Editura AcademieiBucharest, Romania, 1981; (d) K. J. Ivin, “OlefinMetathesis”, Academic Press, London, 1983
3 J.-L. Hérisson and Y. Chauvin, Makromol. Chem.,1971, 141, 161
4 (a) R. R. Schrock, S. M. Rocklage, J. H. Wengrovius,G. Rupprecht and J. Fellmann, J. Mol. Catal., 1980,8, 73; (b) S. M. Rocklage, J. D. Fellmann, G. A.Rupprecht, L. W. Messerle and R. R. Schrock, J.Am. Chem. Soc., 1981, 103, 1440; (c) J. S. Murdzekand R. R. Schrock, Organometallics, 1987, 6, 1373; (d)R. R. Schrock, S. A. Krouse, K. Knoll, J. Feldman,J. S. Murdzek and D. C. Yang, J. Mol. Catal., 1988,46, 243; (e) R. R. Schrock, J. S. Murdzek, G. C.Bazan, J. Robbins, M. DiMare and M. O’Regan, J.Am. Chem. Soc., 1990, 112, 3875; (f) G. C. Bazan, J.H. Oskam, H.-N. Cho, L. Y. Park and R. R.Schrock, J. Am. Chem. Soc., 1991, 113, 6899; (g) R. R.Schrock, Tetrahedron, 1999, 55, 8141; (h) R. R.Schrock, Chem. Rev., 2002, 102, 145; (i) R. R.Schrock, Acc. Chem. Res., 1979, 12, 98
5 (a) S. T. Nguyen, L. K. Johnson and R. H. Grubbs,J. Am. Chem. Soc., 1992, 114, 3974; (b) Z. Wu, S. T.Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. Chem.Soc., 1995, 117, 5503; (c) S. T. Nguyen, R. H. Grubbsand J. W. Ziller, J. Am. Chem. Soc., 1993, 115, 9858;(d) G. C. Fu, S. T. Nguyen and R. H. Grubbs, J. Am.Chem. Soc., 1993, 115, 9856; (e) P. Schwab, M. B.France, J. W. Ziller and R. H. Grubbs, Angew. Chem.Int. Ed., 1995, 34, 2039; (f) P. Schwab, R. H. Grubbsand J. W. Ziller, J. Am. Chem. Soc., 1996, 118, 100; (g)M. Scholl, T. M. Trnka, J. P. Morgan and R. H.Grubbs, Tetrahedron Lett., 1999, 40, 2247
6 (a) R. R. Schrock, in “Ring-Opening Polymerisation:Mechanisms, Catalysis, Structure, Utility”, ed. D. J.Brunelle, Hanser Publishers, München, 1993; (b) V.Dragutan and R. Streck, “Catalytic Polymerizationof Cycloolefins”, Elsevier, Amsterdam, 2000; (c) E.Khosravi and T. Szymanska-Buzar (eds.), “Ring-Opening Metathesis Polymerisation and RelatedChemistry”, Kluwer Academic Publishers,Dordrecht, 2002; (d) “Novel Metathesis Chemistry:Well-Defined Initiator Systems for SpecialtyChemical Synthesis, Tailored Polymers andAdvanced Materials Applications”, eds. Y.Imamoglu and L. Bencze, Kluwer AcademicPublishers, Dordrecht, 2003; (e) “Alkene Metathesisin Organic Synthesis”, ed. A. Fürstner, Springer,Berlin, 1998
7 (a) H. S. Eleuterio, German Patent 1,072,811 (1960);Chem. Abstr., 1961, 55, 16005; (b) H. S. Eleuterio,U.S. Patent 3,074,918 (1963); (c) H. S. Eleuterio, J.Mol. Catal., 1991, 65, 55 and references therein
8 (a) V. Dragutan, A. T. Balaban and M. Dimonie,“Olefin Metathesis and Ring-OpeningPolymerisation of Cyclo-Olefins”, Wiley, New York,1985; (b) K. J. Ivin and J. C. Mol, “Olefin Metathesisand Metathesis Polymerisation”, Academic Press,San Diego, 1997; (c) R. H. Grubbs, “Handbook ofMetathesis”, 3 vols., Wiley-VCH, Weinheim, 2003
9 R. R. Schrock and A. H. Hoveyda, Angew. Chem. Int.Ed., 2003, 42, 4592
10 (a) R. H. Grubbs and S. Chang, Tetrahedron, 1998, 54,4413; (b) T. M. Trnka and R. H. Grubbs, Acc. Chem.Res., 2001, 34, 18; (c) R. H. Grubbs, Tetrahedron,2004, 60, 7117
11 (a) D. Astruc, New J. Chem., 2005, 29, 42; (b) D.Astruc, L’actualité chimique, 2004, (273), 3
12 S. T. Diver and A. J. Giessert, Chem. Rev., 2004, 104,1317
13 T. J. Colacot, Platinum Metals Rev., 2002, 46, (2), 8214 (a) V. Dragutan, I. Dragutan and A. T. Balaban,
Platinum Metals Rev., 2000, 44, (2), 58; (b) V. Dragutan,I. Dragutan and A. T. Balaban, Platinum Metals Rev.,2001, 45, (4), 155; (c) V. Dragutan and I. Dragutan,Platinum Metals Rev., 2004, 48, (4), 148; (d) V. Dragutan,I. Dragutan and F. Verpoort, Platinum Metals Rev., 2005,49, (1), 33; (e) V. Dragutan, I. Dragutan and A.Demonceau, Platinum Metals Rev., 2005, 49, (3), 123
15 (a) A. Fürstner, Top. Organomet. Chem., 1998, 1, 37;(b) S. J. Connon and S. Blechert, Angew. Chem. Int.Ed., 2003, 42, 1900; (c) K. C. Nicolaou, P. G. Bulgerand D. Sarlah, Angew. Chem. Int. Ed., 2005, 44, 4490
Platinum Metals Rev., 2006, 50, (1) 37
The AuthorsValerian Dragutan is a Senior Researcher at the Institute of OrganicChemistry of the Romanian Academy (Splaiul Independentei 202 B,PO Box 35-108, 060023 Bucharest, Romania; E-mail:[email protected]). His research interests are homogeneouscatalysis by transition metals and Lewis acids; olefin metathesisand ROMP of cycloolefins; bioactive organometallic compounds;and mechanisms and stereochemistry of reactions in organic andpolymer chemistry.
Ileana Dragutan is a Senior Researcher at the Institute of OrganicChemistry of the Romanian Academy (E-mail:[email protected]). Her interests are in stable organic freeradicals – syntheses and applications as spin probes, olefinmetathesis, Ru catalysis, transition metal complexes with freeradical ligands and their magnetic and catalytic properties,azasugars and prostaglandin-related drugs.
Alexandru T. Balaban (Texas A&M University Galveston, 5007Avenue U, Galveston, TX 77551, U.S.A.; E-mail:[email protected]) is a member of the Romanian Academy andtaught organic chemistry for over 40 years at BucharestPolytechnic University. He now teaches at Texas A&M University atGalveston. His interests include homogeneous catalysis,heterocyclic compounds, stable free radicals and theoreticalchemistry, including chemical applications of graph theory andtopological indices. Recently he was elected as Honorary Memberof the Hungarian Academy of Science and as President of theInternational Academy of Mathematical Chemistry.
References
38Platinum Metals Rev., 2006, 50, (1), 38–45
The Ninth Grove Fuel Cell Symposium andexhibition was held at the prestigious QueenElizabeth II Conference Centre in Westminster,London, from 4th to 6th October 2005. This bian-nual event is now the largest fuel cell gathering inEurope, this one attracting 480 delegates from 38countries (1, 2). Some 54 papers were presented,and 186 posters were displayed. A further 760 peo-ple attended the associated trade exhibition, and ahalf-day demonstration of fuel cell vehicles andtechnology was held in Trafalgar Square. The latterattracted considerable public and media attention.Because of the wide range of fuel cell types andapplications is now available, this article is restrict-ed mainly to those associated with the utilisation ofthe platinum group metals.
Facts on Global WarmingProfessor Lars Sjunnesson, the Symposium
Chairman, welcomed the delegates and introducedProfessor Sir David King (Chief Scientific Adviserto the U.K. Government) who spoke on ‘TheScience of Climate Change: the Challenge ofGlobal Warming’ (3). As long ago as the 19th cen-tury, noted scientists, such as Fourier and Tyndall,began to speculate about the effects of increasedcarbon dioxide (CO2) in the atmosphere, while in1896 Arrhenius forecast that a doubling of CO2
levels would result in a 5ºC global temperature rise.This agrees well with the latest forecast of a rise of3 to 7ºC. Carbon dioxide levels, having remainedstable at 180-270 parts per million (ppm) for mil-lions of years, currently stand at 379 ppm and areforecast to exceed 500 ppm at our current rate ofconsumption of fossil fuels.
There were an estimated 30,000 fatalities inEurope, in 2003, as a result of high temperatures,but because of global warming, by 2050 the aver-age temperature is likely to equal the 2003extremes. This is one of the main driving forces for
finding more efficient ways to utilise fossil fuelsand seek alternative renewable energy sources.Iceland is leading the way: having decided to moveto a hydrogen economy. In future all vehicles therewill be powered by hydrogen or fuel cells.
Grove Medal PresentationProfessor King then presented the Grove
Medal for 2005 to Alan Lloyd (CaliforniaEnvironmental Protection Agency) who describedhimself as “an environmental person with a job todo” rather than specifically a fuel cell advocate.The quality of air in California has improved inrecent years, however, particulates have alsoincreased. A number of organisations have beenset up to introduce clean energy supplies and cleanvehicles. Some 50 stationary fuel cells totalling 10MW have been installed, and the California FuelCell Partnership is demonstrating a fleet of vehi-cles. The California Hydrogen Highway shouldresult in 50 to 100 hydrogen fuelling stations ableto supply 2000 vehicles by 2010. This fuel networkis being extended up the west coast of the U.S.A.and into Canada. Other areas, in the U.S.A., Japanand Germany, are being equipped with hydrogenrefuelling facilities.
The European PositionProfessor Werner Tillmetz (ZSW, Germany)
surveyed the technology being developed for fuelcells under the 7th Framework Programme organ-ised by the European Commission. Within theEuropean Union (EU), fuel cells are seen asimportant for job creation in the longer term, aswell as facilitating a change to hydrogen and bio-mass fuels to safeguard energy supplies. Over 100light passenger vehicles are in daily use, and 40 fuelcell buses have spent more than 2 years in passen-ger service. Worldwide, more than 350 vehicles areundergoing fleet tests and product development.
DOI: 10.1595/147106705X84287
The Ninth Grove Fuel Cell SymposiumBUILDING AND COMMERCIALISATION OF A FUEL CELL INDUSTRY – A PROGRESS REPORT
Reviewed by Donald S. CameronThe Interact Consultancy, 11 Tredegar Road, Reading RG4 8QE, U.K.; E-mail: [email protected]
Early markets are envisaged for fuel cell motorcycles (see Figure 1) and scooters, go-carts, fork lifttrucks, uninterruptible power supplies, marine andauxiliary power supplies, while military applica-tions represent early niche markets for similarproducts. Over 3500 small portable units havealready been sold for demonstration and nichemarkets. More than 100 units, each of 1-5 kW arecurrently installed in domestic combined heat andpower applications within the EU, and many ofthese are providing over 80% thermal efficiency.These have electricity grid connection.
Michael Fübi (RWE Fuel Cells, Germany) pro-vided an overview of the stationary fuel cellmarket. There is increasing interest in utilisingrenewable energy, with manure, sewerage and farmwastes, coal mine and landfill gases representinghuge untapped energy resources, as well as pre-senting critical disposal problems. Moltencarbonate fuel cells can utilise hydrogen derivedfrom these sources. Several 250 kW plants built byMTU CFC Solutions have been extensivelydemonstrated, and one has been operating on nat-ural gas in Magdeburg, Germany, since December2002, accumulating over 23,500 hours of powergeneration. As operation on natural gas has beensuccessfully demonstrated, a plant running on bio-mass anaerobic digester gas was begun in July2005. Applications for these combined heat andpower units include hospitals, telecommunications
companies, the food industry andsewerage works. For smaller genera-tors of up to 10 kW, there is anestimated demand for 50,000 unitsper year in the EU alone for com-
mercial applications, while a much larger marketexists for smaller fuel cells for residential use.
William Ernst (Plug Power, U.S.A.) describedan early market for small fuel cells in his talk enti-tled ‘Small-Scale Dispersed Stationary Systems - aStatus Report’. Generators of 1-20 kW, most ofwhich are based on polymer electrolyte membrane(PEM) fuel cells catalysed by platinum, are rapidlyfinding an increasing range of uses for cell-phonenetwork supplies, microwave repeater stations,pipeline monitoring stations, and cathodic protec-tion. Plug Power have produced over 500 systemsto date, and the eventual market for this type ofdevice was quoted as $3.6 billion. Even at the cur-rent cost of $3000 kW- 1, economic niche marketsare beginning to emerge as fuel cells can provideunique solutions for standby and auxiliary powersupplies. In the United States, a Federal tax creditof 30% (up to $1000) of the capital cost is helpingto develop a market that is expected to maturebetween 2010 and 2020.
Road Vehicles and Auxiliary Power Supplies
Yuji Kawaguchi (Honda Fuel Cell Power,Japan) gave details of their passenger vehicle devel-opment programme. This was begun in the 1980s,and has culminated in the latest Honda FCX whichis now fully certified for road use, and offered forpublic rental. The high power density fuel cell
Platinum Metals Rev., 2006, 50, (1) 39
Fig. 1 This ENV motorbike,demonstrated by Intelligent Energy,features a 1 kW PEM-type power packfuelled by compressed hydrogen. Thehybrid design, when used in combinationwith lead acid batteries, gives a topspeed of 80 kmph and a range of over160 km. The power pack is easilyremoved for independent use
Platinum Metals Rev., 2006, 50, (1) 40
developed by Honda for the purpose is suitablefor volume production.
For peak power it is augmented by an ultra-capacitor giving a total of 80 kW. The fuel celldevelops 50 kW, has a volume of 33 litres and aweight of 48 kg. It operates at 95ºC and is capableof start-up from -20ºC. This platinum-catalysedfuel cell has an aromatic electrolyte membranecontaining sulfonate groups, providing conductiv-ity twice that of conventional proton exchangemembranes at -20ºC. The stamped metal separa-tor plates have a stainless steel base with anoxidised surface containing electrically conductiveinclusions to provide contact resistance of lessthan one quarter of equivalent carbon plates, andweighing 20% less. Using the stamped separatorshalves the thickness of the cell compared to stan-dard construction methods. Their inherentspringiness means that fewer compression compo-nents are required. The Honda FCX vehicle has aweight of 1670 kg, and range of 430 km on hydro-gen compressed to 350 bar, with a top speed of150 km h–1. The first models were delivered in2002, in Japan and the U.S.A., and one vehicle is inuse in California for personal daily commuting.
Massimo Venturi (NuCellSys, and formerly ofBallard Power Systems, Germany) described theprogress made for buses during various demonstra-
tion programmes. The EU sponsored Clean UrbanTransport Experiment (CUTE) trials involves 30buses, see Figure 2. By July 2005 this fleet hadoperated for 60,000 hours and 850,000 km. The tri-als have shown that fuel cell engines have provenfunctionality and availability in commercial use.Reliability has been dramatically improved, withmean times between failures now about 3 timeslonger than at the start of the trials due to imple-mented improvements. For example, start-up timeshave been improved simply by making changes tocomputer software. Improvements still needed fora fully viable commercial product include longerfuel cell lifetimes (at least 5000 hours), increasedpower density and competitive cost.
Power for Consumer ElectronicsAccording to George Apanel (SRI Consulting,
U.S.A.) consumer electronics could provide one ofthe first large markets for fuel cells and provide arevolution in personal devices. Costs are alreadycompetitive – with rechargeable batteries for manyapplications – and, on a cost per watt basis, are upto 80% lower. At equal weights, fuel cells can pro-vide 5-10 times the operating time of an advancedbattery. However, the main advantage is the abili-ty to recharge fuel cells instantly with a cartridge ofliquid fuel, such as methanol. Commercially viable
Fig. 2 ThisDaimlerChryslerCitaro bus was used atthe Symposium fortaking delegates ontours of London sights.There are three suchfuel cell buses inservice in London. Intotal, 30 such busesare being evaluated inEuropean cities underCUTE, the EuropeanUnion sponsoredClean UrbanTransport Experiment
Platinum Metals Rev., 2006, 50, (1) 41
direct methanol fuel cells (DMFCs) are expected tobe widely available within 2 years, and there is ahuge opportunity provided by the 470 million con-sumer electronic devices sold worldwide. Thismarket is growing at 10% per annum. A DMFCfor portable use is in Figure 3.
Shimshon Gottesfeld (MTI Microfuel Cells,U.S.A.) explained that battery technology has tra-ditionally lagged behind telecommunicationstechnology. Ideally, power supplies with a five-foldpower density are needed for devices such as wire-less local area networks, digital television, hard diskdrives and radio tuners. MTI have developed amethod of operating DMFCs to overcome someof the limitations of this system. By running thesecells at high current density, the methanol oxida-tion reaction reaches zero order. The Pt/Rucatalysed anodes can be fed with concentratedmethanol, which is consumed before it has theopportunity to diffuse to the air cathodes (whichhave 6 mg cm- 2 platinum loadings), where it wouldotherwise cause mixed potentials. In addition,there is a spontaneous transfer of water from thecathode to the anode helping to suppress methanol
diffusion. The cells provide power of 35 mW cm- 2
with 30% conversion efficiency of the fuel. TheseMobion®® cells are being used by an industrial cus-tomer to power a radio frequency identity (RFID)tag reader. The fuel cell has an output of 1 W for35 hours (that is 35 W h), compared to the 8 Whprovided by the normal Li-ion battery.
The high energy density of methanol as an ener-gy store explains the huge increase in interestin these devices in the past few years. TheMobion®® cells yield around 1100 Wh l- 1 at30% conversion efficiency, compared to 200Wh l- 1 for advanced lithium prismatic bat-teries. This provides an enormous incentive and anopportunity for electrical device manufacturers toutilise this higher available power in an even widerrange of devices. In the immediate future, the mil-itary domain is seen as the first large niche marketfor DMFCs from a cost point of view, in applica-tions such as cord-free rechargeable power packtechnologies. Hybrid battery/fuel cell applicationsare ideal since DMFCs are able to provide relative-ly low power outputs for long periods with highampere-hour capacities.
Peter Gray (Johnson MattheyFuel Cells, U.K.) reviewed some ofthe advances made in catalysts andmembrane electrode assemblies(MEAs) for DMFCs, and explainedhow these are underpinning devel-opment of devices for portablepower and consumer electronics.Applications being considered forDMFCs include recreational vehi-cles, boats and isolated dwellings, aswell as remotely located telecom-munications stations, traffic signs,weather stations, pipeline monitor-ing, etc. There are huge numbers ofdevices requiring less than 25 W,including laptop computers, per-sonal digital assistants, camcordersand mobile telephones. Theserequire MEAs giving high perfor-mance at temperatures close toambient, and self regulation ofwater and fuel, as well as being of
Methanol isa high energydensity store
Fig. 3 A direct methanol fuel cell produced by Smart Fuel Cell. This wasoperated at the exhibition alongside the Symposium. Its output is 50 W at4 A; methanol consumption is 1.3 l kWh–1; and its overall weight is 8 kg
Platinum Metals Rev., 2006, 50, (1) 42
low cost. Activation polarisation at the methanolelectrode is still the main performance limitationof DMFCs, despite the availability of catalysts,such as carbon supported Pt/Ru with upwards of100 m2 g- 1 surface area, and self-supported Pt/Rualloy catalysts with 70 m2 g- 1. MEAs have demon-strated lifetimes in excess of 4000 hours andpower densities of 100 mW cm- 2. This equates to500 mV at 200 mA cm- 2 at 60ºC - a relatively highoperating voltage that is desirable for good energyconversion efficiency.
Traditionally, the platinum metals industry hasresponded to increased demand for materials byincreasing production. The emergence of the auto-motive catalyst industry posed no problems, andsimilarly, steadily growing demand for fuel cellsshould create no difficulty. Gray emphasised thatthere are substantial reserves of platinum availablefor fuel cell development, and also the fact that atthe end of life, over 90% of the platinum groupmetals can be recovered and recycled. Productscan be designed for ease of metal recovery as wellas efficient manufacture. In fact, according toPhilip Crowson, formerly Chief Economist ofRTZ, at current rates of use, two-thirds of themetals in the Periodic Table will run out beforeplatinum.
Military ApplicationsThe power and energy demands for future U.S.
Army programmes, such as Future Force Warriorand Future Combat System, require a revolution inpower supplies, and fuel cells are viewed as a tech-nology that may meet many of the military’s powerneeds. Chris Bolton (U.S. Army Research,Development and Engineering Command (RDE-COM)) outlined three applications where fuel cellsare being evaluated for possible military use. Theseare soldier and sensor power (under 100 W), man-portable power sources (100-500 W) and smallmobile power units (0.5-10 kW). Fuel cells largerthan 10 kW face competition from other powersources, such as diesel and Stirling engines. RDE-COM are evaluating fuel cells supplied by anumber of manufacturers and has drawn up pre-liminary specifications for a 20 W tactical powersystem for the Land Warrior Program, with a goal
of 600-700 Wh kg- 1 (including fuel) for a 72-hourmission. However, the life of competing recharge-able batteries is reduced by high ambienttemperatures, experiencing up to a 2-3 folddecrease in extreme environments, which furtherrenders fuel cells even more economic as batteryreplacements.
George Cipriano (Protonex, U.S.A.) outlinedsome of their work on direct and reformedmethanol fuel cells. Most of these are hybrid sys-tems with batteries providing peak power, in a sizerange of 10-500 W. One 30 W continuous PEMfuel cell man-portable system designed for a 72-hour mission operates on sodium borohydride fuelwhich is decomposed to provide hydrogen whenrequired. This provides an energy density of 380Wh kg- 1, compared to 150 Wh kg- 1 for lithiumbatteries and 130 Wh kg- 1 for rechargeable cells.Further developments are projected to increasethe fuel cell energy density to 800-1000 Wh kg- 1.One major contrast with battery power is that formissions of longer duration, the fuel cell unitremains the same, and only additional fuel car-tridges need to be carried.
The use of portable fuel cell battery chargersfor frontline soldiers is also being evaluated by theBritish Ministry of Defence, according to AngusJohnson (Thales Ltd., U.K.). Typically, a companyof soldiers requires 183 batteries for a 48-hourfrontline mission on the battlefield, under a widevariety of environments.
Great advances in reliability and safety enablefuel cells to be the sole power source for anew generation of submarines. S.Krummrich (HDW Fuel Cell SystemsGmbH, Germany) stated that at least 16Type U212A boats are being supplied to a numberof navies, including those of Germany, Greece,Italy, Portugal and South Korea. These boats useplatinum-catalysed PEM fuel cell modules, each of72 cells, made by Siemens. Nine of these providearound 30 kW each, operating at 70-90ºC withfuel conversion efficiencies of 72% at 20% ofrated load and 62% at full load. Hydrogen fuel isstored on board the vessel in the form of hydrides,while the oxidant is liquid oxygen. The wholepropulsion system must be self-contained, with
Navies usingfuel cellsubmarines
Platinum Metals Rev., 2006, 50, (1) 43
provision for disposing of waste heat, productwater, purge gases, etc. Product water, for exam-ple, is used during the whole mission for thesanitary equipment on board. The fuel cell mod-ules are connected in series by diodes using doublebus bars to eliminate magnetic fields, and a hybridarrangement with conventional lead-acid batteriesis used for high speed operation. The propulsionload defines the main bus bar voltage, and the sys-tem normally operates using only the fuel cellassembly. For high current demands, as the busbar voltage falls, an increasing load is taken fromthe batteries in combination with the fuel cells.
Darren Browning (DSTL, U.K.) outlined theirprogramme on fuel cells for a variety of mil-itary applications, including propulsionsystems for unmanned underwater vessels,unmanned aerial vehicles, sonobuoys and
army equipment. Their target specification is600-1000 Wh kg- 1, which is 5 to 6 times the ener-gy density of silver-zinc or lithium-ion batteries.For a variety of reasons, direct borohydride fuelcells have been selected for development. Sodiumand potassium borohydrides are stable in highlyalkaline solution, and these are used in alkalineelectrolyte fuel cells with Pt/C catalysts for thecathode and an anion exchange membrane. Forthe anode catalyst, several materials have beenevaluated, the optimum being high surface areagold dispersed on carbon, which exhibits goodelectrochemical activity, but low rates of sponta-neous borohydride hydrolysis. In comparison,Pt/Ru or Au/Pt catalysts provide higher anodeactivity than gold, but hydrolyse the reagent. Workis underway to synthesise and evaluate suitableanionic membrane materials to minimise borohy-dride migration to the cathode.
A fleet of residential proton exchange mem-brane fuel cells, produced by manufacturersin the U.S.A., is being evaluated at militaryand civil facilities by the U.S. ArmyEngineer Research and Development
Center/Construction Engineering ResearchLaboratory (ERDC/CERL). These premisesinclude office buildings, hospitals, industrial facili-ties, barracks and gymnasiums, etc., all of whichcan benefit from improved power generation effi-
ciency and security of supply. M. White (JonesTechnologies, Inc., U.S.A.) introduced some oftheir preliminary findings. Domestically-producedproton exchange membrane fuel cells of 1-20 kWoutput are being evaluated at various U.S. militaryinstallations and embassies. Their manufacturersinclude Idatech, Plug Power, Nuvera, ReliOn, andLogan Energy. One fuel cell will be installed in theU.S. Embassy in Grosvenor Square, London. Agreat diversity of installations is being sought; unitsare required to provide a minimum of one year offuel cell power with at least 90% availability.Although the program has been running for 4 fis-cal years, delays in implementation mean thatresults are only available from the first two years.A total of 92 fuel cells will be sited at 56 DoD facil-ities. Results from 34 fuel cells at 24 sites are so faravailable.
The fuel cell units have achieved 82–90% relia-bility, although not all the units have completedthe one-year demonstration. Overall, the projecthas accumulated 115,000 operating hours, with anaverage conversion efficiency for natural gas of31.7%. The most commonly replaced componentswere steam filters, pumps, and supply lines, whilethe second most common were water filters,including reverse osmosis units, carbon filters, de-ionising units and other associated parts. Fuel cellstacks were replaced on average after 2485 hours,although 4 of the 11 natural gas fired units that ranfor over a year did not require replacement stacks.One stack has operated for over 10,250 hours todate. All of the stack replacements took placebefore they failed completely. However, it hasbeen concluded that the weakest parts of theinstallation are the steam and filtration systems.The study will continue for at least another twoyears, and improvements in designs resulting frominformation feedback should considerablyimprove the systems during this time.
Residential Combined Heat and PowerSmall fuel cells are being demonstrated as a pre-
lude to commercial exploitation. J. Heinen (RWEFuel Cells GmbH, Germany) explained they areone of the companies active in this field, with part-ners BBT Thermotechnik (Germany) and IdaTech
Militarypropulsionsystems
Residentialmilitaryuses
Platinum Metals Rev., 2006, 50, (1) 44
LLC (U.S.A.). Currently, twelve 4.6 kW units arebeing evaluated in multi-family houses and smallcommercial applications, with a further 25 unitsplanned for the end of the year. Operating on nat-ural gas, they provide 30% conversion of naturalgas to electricity, with an overall 80–83% efficien-cy including heat recovery. The devices can beconnected to the electric utility grid to enable opti-mum utilisation of the generating capacity. RWE isexploring the possibility of acting as an energy ser-vice supplier who owns and maintains the devices,selling electricity and heat to the consumer.
Individual HomesThe single family house is also a possible mar-
ket for fuel cells. In his talk entitled ‘MicroCombined Heat and Power Generation’, G.Gummert (european fuel cell gmbh, Germany,now part of the Baxi Group) detailed their pro-gramme to develop residential fuel cells. Thepotential scale of this market is illustrated by thefact that Baxi produce 800,000 central heatingboilers and 500,000 water heaters annually. A 1.5kW reformer/proton exchange membrane fuelcell system has been developed, and provides anadditional 3 kW of recovered heat. Natural gas,their preferred fuel, is now supplied to 75% ofnew houses in Europe. While 1.5 kW represents70% of the total power requirements, 3 kW pro-vides 65% of the need for heat.
M. Kawamara (Tokyo Gas, Japan) describedthe Japanese national effort to develop protonexchange membrane fuel cell systems for residen-tial applications. One was installed in the JapanesePrime Minister’s official residence in April 2005.The units, built by Matsushita Electric IndustrialCo. Ltd. and Ebara Ballard Corporation, consist ofa 1 kW reformer/fuel cell unit and a hot waterunit. The device is grid connected, with an invert-er to provide AC mains power for the consumer.A 200 litre storage tank provides hot water fordomestic use. Over 400 units have been built thisyear; 175 were installed in the first 6 months. It isplanned to build up to 10,000 units by 2008, andtens of thousands of units after 2010. Ultimately,the Japanese market is seen as up to 1.5 millionunits per year at prices of less than $10,000 each.
The Future of Fuel Cells andHydrogen
The final session of the Symposium looked for-ward to the challenges and future prospects forhydrogen and fuel cells. Pablo Fernandez-Ruiz, amember of the Advisory Council of the Hydrogenand Fuel Cell Technology Platform of theEuropean Commission in Belgium, stressed thatthe EU currently imports 50% of its energy needs,which is forecast to rise to 70% by 2030. In aneffort to stem this rise, under the 7th FrameworkProgramme for 2007-2013, EU funding for ener-gy research will be doubled to 10 billion Euros,with basic research attracting 1.5 billion per year.
Valri Lightner (U.S. Department of Energy)detailed the Hydrogen Fuel Initiative which com-mits $1.7 billion for the first five years(2004-2008) of which $1.2 billion is for the reali-sation of the hydrogen economy and fuel cells.The United States is focusing on energy supplies,particularly the energy needs for transportation, astwo-thirds of oil is used for this purpose.Surprisingly, heavy vehicles and light trucksaccount for higher fuel usage than private cars.Natural gas is one of the best distributed andcheapest sources of energy for hydrogen produc-tion in the U.S.A., while coal (combined with CO2
sequestration) is also regarded as a potential fuel.Fuel cell costs need to be reduced to a target ofaround $30 kW- 1, compared to a current estimat-ed cost of $110 kW- 1, when a production rate of500,000 units per year is assumed. The barriers toachieving wide scale deployment of fuel cells arethought to be codes and standards, the investmentrequired for a hydrogen generation and distribu-tion network, and educating the public, rather thanany technical hurdle.
SummaryA host of manufacturers of fuel cells, compo-
nents and associated equipment is emerging, andmany of their products were exhibited at theSymposium. Small fuel cells of up to 5 kW arealready finding niche markets as standby generatorsin residential combined heat and power applica-tions and consumer electronics. In the latterexample, there are considerable incentives for con-
Platinum Metals Rev., 2006, 50, (1) 45
sumers, and customers are likely to be willing to paya premium price. However, it is evident that costsmust be substantially reduced for widespread trans-port applications to emerge, even for buses. But forstationary applications, increasing manufacturingcapacity is likely to reduce costs considerably.
Associated Exhibitions and Demonstrations
On the afternoon preceding the Symposium, ademonstration of fuel cell technology was held inTrafalgar Square. This attracted wide public andpress interest, and included an Intelligent Energymotorcycle (Figure 1), a DaimlerChrysler Citarofuel cell bus (Figure 2), a DaimlerChrysler F-CellA-class car (Figure 4), a BOC Echo2O car, aMicrocab fuel cell taxi, and a Ballard Airgen unit,and on a trailer the London Hydrogen Partnershipfuel cell, and a Tees Valley fuel cell poweredmobile information sign. The exhibition included alarge marquee open to the public containing a hostof displays and smaller exhibits including: MTUCFC Solutions, Baxi Group, siGEN, JohnsonMatthey, three U.K. universities, Ceres Power,Voller Energy, the London Hydrogen Partnership,and Transport for London. Fuel Cells Canada fea-tured a Scalectrix miniature racetrack which theadults present reluctantly allowed children to use.
The Trafalgar Square exhibits were later movedto the Queen Elizabeth Conference Centre wherethe exhibition attracted over 85 organisations,
including fuel cell manufacturers(many with working demonstra-tions), component suppliers andusers. The DaimlerChrysler bus
proved very popular, taking delegates for regularsightseeing tours around London.
A special edition of the Journal of Power Sources,will carry the full papers.
Bibliography1 Grove Fuel Cell, http://www.grovefuelcell.com/2 A list of previous Grove Fuel Cell Symposium
reviews published in Platinum Metals Review can befound at: http://www.platinummetalsreview.com/,and published as Ref. 2 in D. S. Cameron, PlatinumMetals Rev., 2005, 49, (1), 16 and references therein
3 David King, OST: Chief Scientific Adviser (CSA),U.K., http://www.ost.gov.uk/about_ost/csa.htm
The Reviewer
Don Cameron is an IndependentConsultant on the technology of fuelcells and electrolysers. He is amember of several Working Groups ofthe International ElectrotechnicalCommission, Technical Committee105 on fuel cell standards. He is alsoSecretary of the Grove SymposiumSteering Committee.
Other fuel cell conferences can be found by visitingthe PMR Events Calendar and browsing the listingsor selecting ‘Fuel Cells’ from the drop down menuat:http://www.platinummetalsreview.com/dynamic/event/listA list of all PMR fuel cell articles is freely available at:http://www.fuelcelltoday.com/FuelCellToday/PMRLinks
Fig. 4 This DaimlerChrysler F-Cell A-Class vehicle was driven around inLondon. It is one of 60 such vehiclesalready in use
PROPERTIESNanoscale Precipitates and Phase Transformationsin a Rapidly-Solidified Fe–Pt–B Amorphous AlloyD. V. LOUZGUINE-LUZGIN, W. ZHANG and A. INOUE, J. AlloysCompd., 2005, 402, (1–2), 78–83
XRD and calorimetry were used to study the phasetransformations on heating of rapidly solidified(Fe0.75Pt0.25)75B25. TEM established the existence ofnano-scale cubic cF4 Fe(Pt) solid solution particleswithin the as-solidified amorphous matrix. The parti-cles of the cF4 Fe(Pt) phase start growing at elevatedtemperature and undergo ordering to form a tP4 FePtcompound followed by the precipitation of a tI12Fe2B phase from the residual amorphous matrix.
The High-Pressure Modification of CePtSn –Synthesis, Structure, and Magnetic PropertiesJ. F. RIECKEN, G. HEYMANN, T. SOLTNER, R.-D. HOFFMANN, H.HUPPERTZ, D. JOHRENDT and R. PÖTTGEN, Z. Naturforsch.,2005, 60b, (8), 821–830
High-pressure (HP) modification of CePtSn wascarried out under multianvil high pressure (9.2 GPa)and high temperature (1325 K) conditions from thenormal-pressure modification. Both modifications arebuilt up from Pt centred trigonal prisms. Together,the Pt and Sn atoms form different 3D [PtSn] net-works in which the Ce atoms fill channels.Susceptibility measurements of HP-CePtSn indicateCurie-Weiss behaviour above 40 K with an experi-mental magnetic moment of 2.55(1) µB/Ce atom,indicating trivalent Ce.
Chemical Synthesis and Magnetic Properties ofWell-Coupled FePt/Fe Composite NanotubesH. L. SU, S. L. TANG, N. J. TANG, R. L. WANG, M. LU and Y. W.DU, Nanotechnology, 2005, 16, (10), 2124-2128
Heating a porous Al2O3 template loaded with analcohol solution of a Fe chloride and Pt chloride mix-ture in flowing H2 at 670ºC gave L10 FePt nanotubes(1). FePt/Fe composite nanotubes were thenobtained by reducing the alcohol solution of the Fechloride within (1) at 470ºC. For (FePt)100–x/Fex (x =0–26 at.%), the hard and soft phases were well cou-pled and the coercivity was tunable over 1.27–2.73 T.
Heats of Displacement of Hydrogen fromPalladium by Noble GasesA. J. GROSZEK, E. LALIK and J. HABER, Appl. Surf. Sci., 2005,252, (3), 654–659
Noble gases (He, Ne, Ar) produced heat evolutionwhen contacted with Pd powder partially saturatedwith H. The noble gases displace the adsorbed Hspecies from the Pd surface, causing their reabsorp-tion in the Pd lattice with the exothermic heat ofPd–H bond formation, or the formation of H2.
Properties of the Quaternary Amorphous AlloyPd40Ni40B10P10
Q. LI, D. GREIG, S. H. KILCOYNE, P. J. HINE, J. A. D. MATTHEWand G. BEAMSON, Mater. Sci. Eng. A, 2005, 408, (1–2),154–157
The title alloy (1) was prepared in bulk form, with-out the use of B2O3 flux, by 50% substitution of B forP in the Pd40Ni40P20 system. (1) was shown to be large-ly amorphous by neutron and X-ray diffraction andDSC. The XPS data suggest partial substitution of Bfor P. With the addition of B, glass-forming abilitywithout any fluxing compound was demonstrated.
Stress Evolution in Sputter-Deposited Fe–PdShape-Memory Thin FilmsY. SUGIMURA, I. COHEN-KARNI, P. McCLUSKEY and J. J.VLASSAK, J. Mater. Res., 2005, 20, (9), 2279–2287
Fe-26–30 at.% Pd films (1) were deposited by mag-netron sputtering. (1) are highly supersaturated solidsolutions of Pd in Fe with a b.c.c. crystal structure andvery fine grain size. (1) undergo an irreversible densi-fication at > 100ºC. The high-temperature austenitephase can be retained at low temperature by anneal-ing (1) at 900°C followed by rapid cooling.Depending on the composition of (1), the metastableaustenitic phase transforms to either a b.c.t. or a f.c.t.martensite at ~ room temperature. Formation of thef.c.t. martensite is reversible.
Reactive Diffusion between Pd and Sn at Solid-State TemperaturesT. TAKENAKA, M. KAJIHARA, N. KUROKAWA and K.SAKAMOTO, Mater. Sci. Eng. A, 2005, 406, (1–2), 134–141
Sn/Pd/Sn diffusion couples (1) were prepared by adiffusion bonding technique. (1) were isothermallyannealed between T = 433 and 473 K for varioustimes in a silicone oil bath. PdSn4, PdSn3 and PdSn2
compound layers were observed at T = 433 K, butonly PdSn4 and PdSn3 layers were found at T = 453and 473 K. Volume diffusion was the rate-controllingprocess of the reactive diffusion between Pd and Sn.
Saturated Solid-Solution Hardening Behavior ofIr–Hf–Nb Refractory Superalloys for Ultra-HighTemperature ApplicationsJ. B. SHA and Y. YAMABE-MITARAI, Scr. Mater., 2006, 54, (1),115–119
In Ir-3Hf-xNb the solubility limitation of solutes Hfand Nb in the Ir solid solution is close to Ir-3Hf-5Nb(1). (1) has a monolithic saturated f.c.c. structure, anda 0.2% yield strength of 140 MPa, even at 1950ºC,compared with 19.7 MPa for pure Ir. A large solid-solution hardening effect is obtained in the Ir alloys,in which the solutes have a large misfit parameterwith Ir and a small solubility limitation.
Platinum Metals Rev., 2006, 50, (1), 46–49 46
ABSTRACTSof current literature on the platinum metals and their alloys
DOI: 10.1595/147106706X96012
CHEMICAL COMPOUNDSSolvent-Induced Supramolecular Isomerism in[Pt(S=C(NH2)2)4]2+ Croconate SaltsP. A. GALE, M. E. LIGHT and R. QUESADA, Chem. Commun.,2005, (47), 5864–5866
Slow diffusion of acetone into a 1:1 mixture oftetrakis(thiourea)Pt(II) dichloride and croconic aciddisodium salt in DMSO–H2O gave crystals of[Pt(SC(NH2)2)4][C5O5]·4DMSO (1). (1) forms a 3DH-bonded assembly containing two types of channelsthat accommodate the solvent molecules. TheDMSO molecules within the smaller channels areheld by two H bonds; the larger channels contain sol-vent held by only one H bond.
Reaction of [(C6H6)RuCl2]2 with 7,8-Benzoquinoline and 8-HydroxyquinolineJ. G. MALECKI, M. JAWORSKA, R. KRUSZYNSKI and J. KLAK,Polyhedron, 2005, 24, (18), 3012–3021
[(C6H6)RuCl2]2 was reacted with 7,8-benzoquinolineand 8-hydroxyquinoline in MeOH. The magneticproperties of [Ru(C9H6NO)3]·MeOH (1) relate to theantiferromagnetic coupling of the Ru centres in thecrystal lattice. The EPR spectrum of (1) indicates asingle isotropic line only, characteristic of Ru3+, withspin equal to 1/2.
ELECTROCHEMISTRYLight-Assisted Synthesis of Pt-Zn PorphyrinNanocomposites and Their Use forElectrochemical Detection of OrganohalidesW. WIYARATN, S. HRAPOVIC, Y. LIU, W. SURAREUNGCHAI andJ. H. T. LUONG, Anal. Chem., 2005, 77, (17), 5742–5749
Pt-Zn porphyrin nanocomposites (1) were synthe-sised using zinc porphyrin and H2PtCl6 in thepresence of light and ascorbic acid. The Pt nanoparti-cles were embedded within the Zn porphyrin matrix.A glassy C electrode was modified with Nafion-sta-bilised (1) and used for dehalogenation of carbontetrachloride, chloroform, pentachlorophenol,chlorobenzene and hexachlorobenzene. The modi-fied electrode exhibited catalytic activity for thereduction of the organohalides at –1.0 V vs.Ag/AgCl.
Electrochemical Behaviour of Amorphous andNanoquasicrystalline Zr–Pd and Zr–Pt Alloys inDifferent EnvironmentsK. MONDAL, B. S. MURTY and U. K. CHATTERJEE, Corros. Sci.,2005, 47, (11), 2619–2635
Melt spun amorphous and nanoquasicrystallineZr70Pd30 (1) and Zr80Pt20 (2) alloy ribbons show bettercorrosion resistance than Zr in all solutions studied.Both are susceptible to chloride attack and pitting hasbeen observed. Complete passivation was observed inH2SO4, while gradual breakdown of the passivatinglayer occurs in NaOH. In general, the nanoquasicrys-talline state in (1) and (2) shows better corrosionresistance than the amorphous state.
PHOTOCONVERSIONRed Electrophosphorescence of ConjugatedOrganoplatinum(II) Polymers Prepared via DirectMetalation of Poly(fluorene-co-tetraphenyl-porphyrin) CopolymersQ. HOU, Y. ZHANG, F. LI, J. PENG and Y. CAO, Organometallics,2005, 24, (19), 4509–4518
PL decay studies indicated that polyfluorene-co-tetraphenylporphyrin Pt(II) (PFO-PtTPP) is a tripletemitter. EL emission from the fluorene segment wascompletely quenched for copolymers with PtTPPcontent as low as 0.5 mol%. The external quantumefficiency of ITO/PEDT/PVK/PFO-PtTPP (1mol%) + PBD (40 wt.%)/Ba/Al was 0.43%.
Single-Layer Electroluminescent Devices andPhotoinduced Hydrogen Production from an IonicIridium(III) ComplexM. S. LOWRY, J. I. GOLDSMITH, J. D. SLINKER, R. ROHL, R. A.PASCAL, G. G. MALLIARAS and S. BERNHARD, Chem. Mater.,2005, 17, (23), 5712–5719
[Ir(dF(CF3)ppy)2(dtbbpy)](PF6) (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine; dtbbpy= 4,4'-di-tert-butyl-2,2'-dipyridyl) can be used as achromophore in single-layer electroluminescentdevices and as a photosensitiser for H2 production.The blue-green electroluminescent emission (500 nm)and relative quantum yield of H2 (2025 µmol H2) wereat the time of publication the highest values to date.
Synthesis, Characterization and Fabrication ofSolar Cells Making Use of [Ru(dcbpy)(tptz)X]X(Where X = Cl–, SCN–, CN–) ComplexesS. ANANDAN, S. LATHA, S. MURUGESAN, J. MADHAVAN, B.MUTHURAAMAN and P. MARUTHAMUTHU, Sol. Energy, 2005,79, (5), 440–448
Dye-sensitised TiO2 solar cells were fabricated using[Ru(dcbpy)(tptz)X]X (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine; tptz = 2,4,6-tris(2-pyridyl)-s-triazine; X =Cl–, SCN–, CN–) attached to sol gel processed TiO2
electrodes. The tptz functions as a spectator ligand,whereas the dcbpy functions as the anchoring ligandwith sufficient visible light absorption.
SURFACE COATINGSAl–Pt MOCVD Coatings for the Protection ofTi6242 Alloy Against Oxidation at ElevatedTemperatureM. DELMAS, D. POQUILLON, Y. KIHN and C. VAHLAS, Surf. Coat.Technol., 2005, 200, (5–6), 1413–1417
Al-Pt coatings (1) were obtained by MOCVD usingMe3(MeCp)Pt and AlH3·N(CH3)2(C2H5). The isother-mal oxidation at 873 K of (1) on Ti6242 coupons wascarried out for 90 h. Oxidation kinetics revealed astrong transient oxidation regime followed by a diffu-sion driven parabolic one. (1) are dense, developscales composed of γ-Al2O3 and δ-Al2O3, and theyprevent Ti diffusion from the alloy to the surface.
Platinum Metals Rev., 2006, 50, (1) 47
HETEROGENEOUS CATALYSISXAFS Characterization of Pt-Fe/Zeolite Catalystsfor Preferential Oxidation of CO in Hydrogen FuelGasesM. KOTOBUKI, T. SHIDO, M. TADA, H. UCHIDA, H. YAMASHITA,Y. IWASAWA and M. WATANABE, Catal. Lett., 2005, 103, (3–4),263–269
Pt-Fe/mordenite catalyst (1) showed high activityand selectivity for the oxidation of CO in H2-rich gascompared with Pt/mordenite. The states of themetallic components in ion-exchanged, H2 pre-treat-ed and post-PROX samples were studied by XAFS.Pt forms metallic clusters after H2 pretreatment or thePROX experiment, whereas a large part of the Feexists as oxides even after H2 treatment. PreferentialCO adsorption onto Pt on (1) was demonstrated.
Characterization and Catalytic Performance of aBimetallic Pt–Sn/HZSM-5 Catalyst Used inDenitratation of Drinking WaterR. RODRÍGUEZ, C. PFAFF, L. MELO and P. BETANCOURT, Catal.Today, 2005, 107–108, 100–105
Pt-Sn/HZSM-5 zeolite (1) was characterised byTPR, H2 chemisorption, XPS and 119Sn Mössbauerspectroscopy to examine its role during the catalyticreducton of nitrate ions in H2O (denitration). Thesetechniques showed a significant decrease in the H:Ptratio upon Sn addition, Sn surface enrichment, theformation of PtSn alloys and Pt catalysis of the Snreduction. (1) exhibits high catalytic activity for thereduction of nitrate to form N2. The role of Sn is toreduce nitrate or nitrite according to a redox process,while the Pt maintains Sn in the metallic state.
Catalytic Activities of Pd-TiO2 Film Towards theOxidation of Formic AcidB. XIE, Y. XIONG, R. CHEN, J. CHEN and P. CAI, Catal. Commun.,2005, 6, (11), 699–704
Pd-TiO2/ITO films (1) were prepared by a dip-coating and subsequent photodeposition (UV light)procedure. (1) were characterised by XRD, SEM andopen circuit voltage. (1) not only exhibited higherphotocatalytic and photoelectrocatalytic activities,compared with a TiO2/ITO film, but also showednon-photocatalytic activity towards HCOOH degra-dation at room temperature and atmosphere pressure.
Catalytic Properties of Several Supported Pd(II)Complexes for Suzuki Coupling ReactionsO. VASSYLYEV, J. CHEN, A. P. PANARELLO and J. G. KHINAST,Tetrahedron Lett., 2005, 46, (40), 6865–6869
Pd(II) complexes with N-ligands were synthesisedand tested for the Suzuki coupling reaction. Thesecomplexes were also heterogenised on silica.Immobilised dichloro(N-(3'-trimethoxysilyl)propyl-1,2-ethanediamine-N,N' )-Pd showed high catalyticactivity, which makes it a useful system for biarylcompound synthesis. Leaching of the Pd intoDMA/H2O was negligible.
HOMOGENEOUS CATALYSISSynthesis, Reaction, and Recycle of FluorousPalladium Catalysts for an Asymmetric AllylicAlkylation without Using Fluorous SolventsT. MINO, Y. SATO, A. SAITO, Y. TANAKA, H. SAOTOME, M.SAKAMOTO and T.FUJITA, J. Org. Chem., 2005, 70, (20),7979–7984
A chiral fluorous aminophosphine (1) bearing twofluorous ponytails was prepared from (S)-prolinol andapplied to the Pd-catalysed asymmetric allylic alkyla-tion of 1,3-diphenyl-2-propenyl acetate with a dialkylmalonate/N,O-bis(trimethylsilyl)acetamide/LiOAcsystem with ≤ 97% ee. The Pd catalyst formed from(1) and [Pd(η3-C3H5)Cl]2 was easily separated fromthe reaction mixture and could be reused five times.
Heck and Suzuki Coupling Reactions in WaterUsing Poly(2-oxazoline)s Functionalized withPalladium Carbene Complexes as Soluble,Amphiphilic Polymer SupportsD. SCHÖNFELDER, O. NUYKEN and R. WEBERSKIRCH, J.Organomet. Chem., 2005, 690, (21–22), 4648–4655
Three amphiphilic, H2O-soluble diblock copoly-mers based on 2-oxazoline derivatives with pendantN-heterocyclic carbene/Pd catalysts in the hydropho-bic block (1) were investigated. (1) in the Heckcoupling of iodobenzene with styrene in neat H2Ogave high activities with TOF ≤ 2700 h–1 at 110ºC.The Suzuki coupling of phenylboronic acid withiodobenzene and bromoarenes in neat H2O exhibitedeven higher catalytic activity with TOF ≤ 5200 h–1 at80ºC.
A Preparative Route to Methyl 3-(Heteroaryl)-acrylates Using Heck MethodologyT. J. KWOK and J. A. VIRGILIO, Org. Process Res. Dev., 2005,9, (5), 694–696
Methyl 3-(heteroaryl)acrylates were prepared usingHeck coupling of heteroarene halides with methylacrylate catalysed by Pd(OAc)2/P(OCH3)3. A 3-foldexcess of methyl acrylate and a bromoheteroarene inDMF were heated under N2 with either triethylamineor diisopropylethylamine. P(OCH3)3 and Pd(OAc)2
were used in a 2:1 ratio with a catalyst loading of 1–5mol%. The highly volatile P(OCH3)3 is readily sepa-rated during the removal of the DMF.
Palladium Catalysed Aryl Amination Reactions inSupercritical Carbon DioxideC. J. SMITH, M. W. S. TSANG, A. B. HOLMES, R. L. DANHEISER andJ. W. TESTER, Org. Biomol. Chem., 2005, 3, (20), 3767–3781
Pd-catalysed C–N bond formation in sc-CO2 hasbeen achieved. Formation of carbamic acid wasavoided by the use of an N-silylamine as the couplingpartner. The system Pd2dba3 (1 mol%) with X-Phos (2mol%) enabled the catalytic amination of aryl bro-mides and chlorides with N-silylanilines. Themethodology was extended to N-arylation of N-silyl-diarylamines, N-silylazoles and N-silylsulfonamides.
Platinum Metals Rev., 2006, 50, (1) 48
Microwave-Assisted Organic Synthesis: Scale-Upof Palladium-Catalyzed Aminations Using Single-Mode and Multi-Mode Microwave EquipmentK. T. J. LOONES, B. U. W. MAES, G. ROMBOUTS, S. HOSTYN andG. DIELS, Tetrahedron, 2005, 61, (43), 10338–10348
Batchwise scale-up of Buchwald-Hartwig amina-tions under microwave irradiation was investigated.Pd(OAc)2 was combined with 2-(dicyclohexylphos-phanyl)biphenyl or 2-(di-t-butylphospanyl)biphenyl.Multi-mode (several vessels irradiated in parallel perbatch) as well as single-mode (one vessel irradiatedper batch) platforms were successfully used. The sin-gle-mode platform is the most convenient since itallows automatic continuous batchwise production.
FUEL CELLSOptimization of the Sputter-Deposited PlatinumCathode for a Direct Methanol Fuel CellK. MAKINO, K. FURUKAWA, K. OKAJIMA and M. SUDOH,Electrochim. Acta, 2005, 51, (5), 961–965
Electrodes prepared by sputtering Pt onto C clothswere evaluated as the cathodes (1) for DMFCs. Ptloading below 0.25 mg cm–2 achieved higher massactivities than a Pt loading of 0.5 mg cm–2 prepared bythe paste method. However, an increase in Pt loadingreduced the catalyst activity for the ORR. Pt utilisa-tion efficiency was ~ 10 times higher at a Pt loadingof 0.04 mg cm–2. An optimum addition of Nafion to(1) improved the catalyst activity.
Instability of Pt/C Electrocatalysts in ProtonExchange Membrane Fuel CellsP. J. FERREIRA, G. J. LA O’, Y. SHAO-HORN, D. MORGAN, R.MAKHARIA, S. KOCHA and H. A. GASTEIGER, J. Electrochem.Soc., 2005, 152, (11), A2256–A2271
Equilibrium concentrations of dissolved Pt speciesfrom Pt/C electrocatalyst in 0.5 M H2SO4 at 80ºCincreased with applied potential from 0.9 to 1.1 V vs.reversible H electrode. The Pt surface area loss for ashort-stack of PEMFCs, operated at open-circuitvoltage (~ 0.95 V), was higher than another operatedunder load (~ 0.75 V). The formation of soluble Ptspecies (such as Pt2+) is claimed to play an importantrole in Pt surface loss in PEMFC electrodes.
On the Preparation and Stability of BimetallicPtMo/C Anodes for Proton-Exchange MembraneFuel CellsN. P. LEBEDEVA and G. J. M. JANSSEN, Electrochim. Acta, 2005,51, (1), 29–40
Bimetallic PtMo/C (1) electrocatalysts were synthe-sised via reductive coprecipitation with eitherformaldehyde or formic acid as reducing agent. Theelectrochemical behaviour of (1) was characterised byCV in H2SO4 solutions as well as in MEAs. (1) wereshown to be inherently unstable and to suffer fromthe gradual loss of Mo due to its dissolution into theelectrolyte, regardless of whether the components arewell-mixed or present in the segregated phases.
Synthesis of Platinum Nanoparticles and ThenSelf-Assembly on Nafion Membrane to Give aCatalyst Coated MembraneH. TANG, Z. LUO, M. PAN, S. P. JIANG and Z. LIU, J. Chem. Res.,2005, (7), 449–451
A catalyst-coated membrane (1) for a PEMFC withPt loading of 2.8 µg cm–2 was prepared by self-assem-bling charged Pt particles at SO3
– groups on themembrane surface. Proton conductivity of (1) was0.0932 S cm–1. The performance of the self-assembledMEA achieved 2.3 mW cm–2. This corresponds to Ptutilisation of 821 W per 1 g Pt.
MEDICAL USESSurface PEGylation and Ligand ExchangeChemistry of FePt Nanoparticles for BiologicalApplicationsR. HONG, N. O. FISCHER, T. EMRICK and V. M. ROTELLO, Chem.Mater., 2005, 17, (18), 4617–4621
By covering magnetic FePt nanoparticles (1) withPEGylated thiol and dopamine ligands, H2O-soluble(1) of great stability were synthesised. The surfacethiol ligands are readily exchanged with other thiolsbearing chain-end functionalities. The surface bindingof both DNA and protein to (1) was achieved.
Tumour-Inhibiting Platinum(II) Complexes withAminoalcohol Ligands: Biologically ImportantTransformations Studied by MicellarElectrokinetic Chromatography, Nuclear MagneticResonance Spectroscopy and Mass SpectrometryP. SCHLUGA, C. G. HARTINGER, M. GALANSKI, K. MEELICH, A.R. TIMERBAEV and B. K. KEPPLER, Analyst, 2005, 130, (10),1383–1389
(SP-4-2)-Bis[(R)-(–)-2-aminobutanol-κN]dichloroPt(II)and (SP-4-2)-bis[(R)-(–)-2-aminobutanolato-κ2N,O]Pt(II)(1) exhibit a strongly pH-dependent rate of reactionwith guanosine 5'-monophosphate. NMR confirmedthe existence of equilibrium between the ring-openedand ring-closed species. An appreciable increase inbinding in the presence of sodium dodecyl sulfate(SDS) micelles was explained in terms of the activa-tion of (1). There is a shifting of the equilibriumtowards the ring-opened species, induced by adductformation between SDS and (1).
Precipitation Hardening of a Cu-FreeAu–Ag–Pd–In Dental AlloyH.-J. SEOL, K.-H. SON, C.-H YU, Y. H. KWON and H.-I. KIM, J.Alloys Compd., 2005, 402, (1–2), 130–135
Three phases were observed in the solution-treatedtitle alloy (1): (a) Au-Ag based phase with smallamounts of In and Pd as matrix; (b) InPd phase asparticle-like structures; and (c) Pd-rich phase as lamel-lar precipitates. By ageing (1), the very fine Pd-richintergranular precipitates grew toward the grain inte-rior as a lamellar structure, and finally the coarsenedPd-rich precipitates covered a large part of the Au-Agbased matrix.
Platinum Metals Rev., 2006, 50, (1) 49
PHOTOCONVERSIONPhotocatalytic Substrate Active under Visible LightSAINT-GOBAIN GLASS FRANCE World Appl. 2005/102,952
A transparent glass substrate, used for glazing, con-tains a mechanically resistant, long-lasting coating, ofa photocatalytic active compound containing a thinlayer of Pt, Rh or Pd, closely associated with a dopedGaP, CdS, TiO2, etc. An energy jump of 1.55-3.26eV occurs between the upper level of the valenceband and the lower level of the conductive band, cor-responding to a wavelength in the visible field.
APPARATUS AND TECHNIQUETitania Nanotube Arrays for Use as SensorsTHE PENN RES. FOUNDATION U.S. Appl. 2005/224,360
An electrical resistive device (1) for sensing H2 gasincludes: an array of TiO2 nanotubes (1) formed byanodising a Ti layer; and a plurality of Pd (or othernoble metal) clusters on top, mechanically supportedby an integral member. (1) may contain dopant of < 1mass% of Pd, Pt, Ru, Sb, etc. In O2, (1) photocatalyt-ically removes contaminants (liquid crude petroleum,pathogens, etc.) by exposure to radiant energy emit-ted within frequency range from visible to ultraviolet.
Integrated Capacitive Microfluidic SensorsCALIFORNIA INST. TECHNOL. U.S. Appl. 2005/243,500
A microfluidic device for capacitive pressure sens-ing, includes a fluid channel, a cavity region, and apolymer-based membrane in between. Additionally,the device includes two capacitor electrodes, consist-ing of Pt, Au, Al, Cr, Ti and doped polysilicon,coupled to the membrane and the cavity region, andan electrical power source placed between whichcauses an electric field within the cavity region.
VCSEL Structure with Platinum SublayerHONEYWELL INT. INC U.S. Appl. 2005/243,886
A vertical cavity surface emitting laser (VCSEL)with high reflectivity and heat dissipation characteris-tics includes a bottom distributed Bragg reflector (1)on a substrate; a metal layer (2), including a reactionbarrier sublayer of Pt, W and/or Ti interposedbetween (1) and the substrate, forming a compositemirror structure. A patterned dielectric layer may beinterposed between to reduce a deleterious chemicalreaction between (2) and (1).
Ammonia Gas Sensor Having Improved DetectionFIS INC Japanese Appl. 2005-127,743
An NH3 gas sensor, with improved accuracy, com-prises a semiconductor embedding a coil-like heatermade of Pt or a Pt alloy acting as a substrate and aconductor-like electrode in a gas sensitive body (1)formed into a spherical shape. (1) is mainly made ofSn oxide and contains Au, to suppress the distur-bance of NH3 detection output by Pt.
HETEROGENEOUS CATALYSISElimination of Aldehydes by Catalytic OxidationHENKEL KG European Appl. 1,591,156
Aldehydes are eliminated by catalytic oxidation inthe presence of a three-component catalyst compris-ing a catalytic composition of Ru/ZrO2-MOx whereM is Ca, Mn, Cu and/or In; x = 0.2-3, especially0.5-2 (the respective upper and lower limiting valuesare included). The process may be run at relativelymoderate (for example, ambient) temperatures lead-ing to a high conversion rate of aldehydes, thusresulting in harmless degradation products, especiallyCO2 and H2O.
Platinum Catalysts Formed by in Situ ReductionDE NORA ELETTRODI SpA World Appl. 2005/097,314
A C-supported Pt black catalyst (1) is obtained bychemical reduction of in situ-formed Pt dioxide (2) byconversion of dihydrogen hexahydroxyplatinate pre-cursor on a C black support, with an active area of 50m2 g- 1. The reducing agent is H2, formaldehyde, etc.(1) is obtained by variation of pH and/or temperature(120-500ºC) and can be incorporated in a gas diffu-sion electrode or in a coated membrane.
Catalyst Used for the Oxidation of HydrogenBASF AG World Appl. 2005/097,715
A supported catalyst (1) for the oxidation of H2 in ahydrocarbon dehydrogenation process comprises α-Al2O3 carrying 0.01-0.1 wt.% Pt and 0.01-0.1 wt.%Sn, with the Pt:Sn ratio being 1:4 to 1:0.2, relative tothe total weight of the catalyst. Also disclosed aremethods for oxygenating H2 and for dehydrogenatinghydrocarbons using rows of integrated reactors with(1).
Removal of Carbon Monoxide and HydrocarbonsHTE AG World Appl. 2005/102,513
Simultaneous removal of CO and hydrocarbonsfrom O-rich exhaust gases is carried out in the pres-ence of a catalyst (1) containing SnO2 and Pdsupported on a carrier oxide, such as a zeolite, beingin a roentgenographically amorphous or nanoparticleform. (1) contains 3-50 wt.% SnO2; and 0.2-10 wt.%Pd and, optionally, Pt, Rh, Ir and Ru; based on themass proportions relatively to the carrier oxide. (1)may also contain B oxide and/or other promoters.
Catalyst Prepared by Microwave HeatingDOW GLOBAL TECHNOL. World Appl. 2005/102,525
A hydro-oxidation catalyst (1) for the hydro-oxida-tion of a hydrocarbon, preferably a C3-C8 olefin,such as propylene, by O2 in the presence of H2 to thecorresponding partially-oxidised hydrocarbon, suchas propylene oxide is presented. (1) comprises Ptgroup metal(s), and/or Au, Ag, lanthanide rare earthmetals, deposited on a titanosilicate, preferably TS-1,which is prepared by microwave heating.
Platinum Metals Rev., 2006, 50, (1), 50–51 50
NEW PATENTSDOI: 10.1595/147106705X84133
Supported Ruthenium Nanoparticle CatalystUNIV. HONG KONG World Appl. 2005/102,971
Oxidation of alkenes is carried out on Ru nanopar-ticle catalysts (1-100 nm in size), with Mn and Fenanoparticles, grafted on an inert solid support, suchas hydroxyapatite. The reaction yields a cis-1,2-diolfrom an alkene, an oxidant and acid at –78 to 40ºC.The catalyst effects cis-dihydroxylation and oxidativecleavage of alkenes to give the respective cis-diols andcarbonyl products. The catalyst can be separated byfiltration or centrifugation, and reused.
Modified Carbon Supported Palladium CatalystCSIR U.S. Patent 6,963,016
A highly active modified C supported Pd catalyst(1) containing 2-6 wt.% Pd, is produced by thesimultaneous impregnation of activated C with Pdand organic Al precursors, such as Pd chloride and Alisopropoxide, respectively, in a tetraethyl ammoniumhydroxide aqueous solution. (1) is used for thehydrodechlorination of dichlorodifluoromethane toproduce difluoromethane, at 250ºC and a gas hourlyspace velocity of 4800 h- 1.
HOMOGENEOUS CATALYSISPalladium Catalysed IndolisationBOEHRINGER INGELHEIM INT. World Appl. 2005/090,302
Substituted indole compounds (1) were synthesisedby reacting a 2-bromoaniline or 2-chloroaniline witha substituted acetylene in the presence of a Pd(OAc)2
catalyst, 1,1′-bis(di-t-butylphosphino)ferrocene lig-and, and K2CO3 base, in 1-methyl-2-pyrrolidinonesolvent at 110-140ºC. (1) are used in the field ofpharmaceuticals and more specifically in processesfor making substituted indole compounds.
Optically Active PolymersNAT. INST. ADV. IND. SCI. TECHNOL. U.S. Patent 6,962,962
An optically optically active polymer (1) is obtainedby polymerising a chiral alkoxy-substituted phenylacety-lene, such as p-(2-methylbutoxy)phenylacetylene inwhich the 2-methylbutoxy group has chirality, in anorganic solvent, such as triethylamine, in the presenceof [Rh(norbornadiene)Cl]2 catalyst. (1) has a largeroptical rotation than the monomeric compound per seand shows different colours, depending on the organ-ic solvent used: the yellow polymer turns black onexposure to CHCl3, then back to yellow by re-precip-itation from a CHCl3 solution, on MeOH addition.
FUEL CELLSProduction of Platinum-Ruthenium Alloy CatalystHITACHI MAXELL LTD Japanese Appl. 2005-177,661
A Pt-Ru alloy catalyst is made by dissolving a Pt anda Ru salt or complex in an organic alcohol solvent. Cpowder is dispersed in the alcohol solution, which isthen heated while refluxing alcohol. The Pt-Ru/Cpowder is filtered, then heat treated at 300-500ºC inan inert atmosphere. Pt-Ru/C exhibits high activitywhen MeOH is oxidised and used in a fuel cell.
Electrode Catalyst for PEFCs NISSAN MOTOR CO LTD Japanese Appl. 2005-196,972
Electrode catalysts (1) for use in PEFCs are manu-factured by mixing Rh chloride-containing and Ption-containing reversed micelle solutions. Reducingagents, such as hydrazine, Na borohydride, etc., areadded and conductive C supports are dispersed in thesolution for loading composite metal particles ontothe support. (1) have high activity and durability.
ELECTRICAL AND ELECTRONICENGINEERINGFerroelectric Capacitor with a TemplateTEXAS INSTRUMENTS INC U.S. Appl. 2005/230,725
A ferroelectric capacitor (1) comprises: a first elec-trode layer, including Ir, located over a substrate. Anoxide electrode template (2) (20-100 nm thick) islocated on the first electrode layer and includes per-ovskites: SrIrO3, SrRuO3, PbIrO3, PbRuO3, etc. (1)may include a ferroelectric dielectric layer over theoxide electrode template and a second electrode layerover the ferroelectric dielectric layer (2). (1) is used inferroelectric random access memory devices.
TiW Platinum InterconnectANALOG DEVICES INC U.S. Patent 6,956,274
A metallisation stack used as a contact structure inintegrated MEMS devices, particularly optical MEMSand Bio-MEMS, comprises a Ti-W adhesion and abarrier layer (1) with a Pt layer on top. (1) is formedby sputter etching the Pt in Ar, followed by a wetetch in aqua regia using an oxide hardmask.Alternatively, the Ti-W and Pt layers are depositedsequentially and patterned by a single plasma etchprocess with a photoresist mask.
MEDICAL USESRadiopaque and MRI Compatible Nitinol AlloysADV. CARDIOVASC. SYST. INC World Appl. 2005/102,407
A medical device, such as a stent, is made fromradiopaque and magnetic resonance imaging compat-ible alloy, for use with, or implanted in, a body lumen.It has improved radiopacity, retains superelastic andshape memory behaviour, and has a thin strut/wallthickness for high flexibility. The stent is made fromalloy (1) such as Ni-Ti (nitinol), and includes a ternaryelement of Ir, Pt, Pd, Rh, Ru, Au, Re, etc. A balloon-expandable stent made from (1) is claimed.
Supramolecular Photoactivated DNA CleavageVIRGINIA TECH INTELL. PROP. U.S. Patent 6,962,910
Replication of hyperproliferating cells is decreasedby using a supramolecular metal complex as a DNAcleaving agent to transfer charge from MLCT lightabsorbing metal, Ru or Os, to electron acceptormetal, Rh, by a bridging π-acceptor ligand. A bioac-tive MLCT state that can cleave DNA is thusgenerated. The complexes are tunable and can cleaveDNA by low energy light in the absence of O2.
Platinum Metals Rev., 2006, 50, (1) 51
Catalysts play a crucial part in the successfuloperation of many processes, and are a major con-tributor to the overall economics. Preciousmetal-based catalysts are extensively used in chem-ical applications and refining, such as catalyticreforming units utilising platinum or platinum-rhe-nium catalysts. The trend is towards employingcatalysts of even higher activity and stability, so aninstalled catalyst inventory could be worth severalmillion dollars. In a chemical process, even smallchanges in catalyst formulations, preparation tech-niques or operational conditions can stronglyenhance or harm catalyst performance, and hencethe overall process economics.
Today the market place is ever more competi-tive and it is imperative that chemical plantsoperate at maximum efficiency. Additionally, theconditions of operation and regulation in process-ing industries are becoming increasingly severe.This necessitates close cooperation between thecatalyst supplier and the operator, and a solid basisof trust has to be established between them toachieve the maximum benefits. The provision oftechnical service is also a vital aspect of a catalystsuppliers’ remit.
Catalyst abuse, misuse or mal-operation aremajor problems for a catalyst supplier to contendwith. Operating companies have a tendency todownsize, and this can result in chemical proces-sors having less personnel to monitor andsupervise units. The consequence has been anincreasing number of ‘catalyst incidents’. Catalystsuppliers must therefore provide appropriate tech-nical service and after-sales support, and include,for instance, training for operators, troubleshoot-ing if needed, and impartial advice for technicalenquiries. All this is aimed at preventing unplannedshutdowns and premature catalyst change-outs.
The level of technical service should always beagreed between the operator and the catalyst sup-plier at the outset, to share expectations and avoidlater disappointment. As a minimum, the processoperator should expect the catalyst supplier, on a
quarterly basis, to evaluate process data and per-form requisite laboratory analyses of any spentcatalyst samples from the process. This evaluationwill provide the best evidence of events during ser-vice and it remains the most conclusive andreliable means of assessing the condition of usedcatalyst, and how the catalyst has performed andresponded to the operating conditions.
Recommended EvaluationsFor precious metal catalysts the evaluations
should include:• Physical analysis, including the crush strength,pore volume and porosity; the BET and/or themetal surface area should be obtained for compar-ison with typical fresh catalyst batches. This canprovide evidence of sintering throughthermal/hydrothermal ageing mechanisms.• The level of any contaminant on the catalystsurface should be accurately measured (ICP, AA,XRF, etc.) and compared to recommended maxi-mum permissible levels for those particularpoisons. These levels are often based on invalu-able information the catalyst supplier has acquiredthrough years of experience. Catalysts are verysensitive, even to low levels of contaminants infeedstocks being processed. Many common cont-aminants (sulfur, halides, alkalis, heavy metals,etc.) can have a significant deactivating effect onthe achieved activity/selectivity, even if their inletconcentrations are below the level of detection (1).• Finally, a pilot plant or microreactor test of cat-alyst activity and selectivity should be made on aused sample and compared to a retained sample offresh catalyst from the batch provided to the cus-tomer. This will help determine the remaininguseful service life of the catalyst. J. K. DUNLEAVY
Reference1 J. K. Dunleavy, Platinum Metals Rev., 2005, 49, (3), 156
The AuthorDr John Dunleavy is a Business Director in the Oil & Gas Section,Johnson Matthey PCT, PO Box 1, Belasis Avenue, Billingham TS231LB, U.K. with over 20 years’ working in the catalyst industry.
![Page 1: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/1.jpg)
![Page 2: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/2.jpg)
![Page 3: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/3.jpg)
![Page 4: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/4.jpg)
![Page 5: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/5.jpg)
![Page 6: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/6.jpg)
![Page 7: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/7.jpg)
![Page 8: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/8.jpg)
![Page 9: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/9.jpg)
![Page 10: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/10.jpg)
![Page 11: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/11.jpg)
![Page 12: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/12.jpg)
![Page 13: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/13.jpg)
![Page 14: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/14.jpg)
![Page 15: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/15.jpg)
![Page 16: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/16.jpg)
![Page 17: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/17.jpg)
![Page 18: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/18.jpg)
![Page 19: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/19.jpg)
![Page 20: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/20.jpg)
![Page 21: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/21.jpg)
![Page 22: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/22.jpg)
![Page 23: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/23.jpg)
![Page 24: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/24.jpg)
![Page 25: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/25.jpg)
![Page 26: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/26.jpg)
![Page 27: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/27.jpg)
![Page 28: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/28.jpg)
![Page 29: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/29.jpg)
![Page 30: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/30.jpg)
![Page 31: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/31.jpg)
![Page 32: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/32.jpg)
![Page 33: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/33.jpg)
![Page 34: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/34.jpg)
![Page 35: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/35.jpg)
![Page 36: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/36.jpg)
![Page 37: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/37.jpg)
![Page 38: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/38.jpg)
![Page 39: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/39.jpg)
![Page 40: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/40.jpg)
![Page 41: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/41.jpg)
![Page 42: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/42.jpg)
![Page 43: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/43.jpg)
![Page 44: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/44.jpg)
![Page 45: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/45.jpg)
![Page 46: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/46.jpg)
![Page 47: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/47.jpg)
![Page 48: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/48.jpg)
![Page 49: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/49.jpg)
![Page 50: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/50.jpg)
![Page 51: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/51.jpg)
![Page 52: PLATINUM METALS REVIEW...Platinum Metals Rev., 2006, 50, (1) 3 Table I Spectral, Electrochemical and Acid-Dissociation Constants for Common [RuIII(pac)(H 2O)] Complexes Complex Spectral](https://reader033.documents.pub/reader033/viewer/2022053111/60850c88ec6252447b659ab2/html5/thumbnails/52.jpg)
