PLATINUM METALS REVIEW · -0.4V .0.1 toQJV 42 t0o.4~ YE. SM. $-0- Glucose Gluconolacton Ascor ba te...

UK ISSN 0032-1400

PLATINUM METALS REVIEW

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VOL. 39 APRIL 1995

Contents

Osmium Bipyridyl Redox Polymers Used in Enzyme Electrodes

Ligand-Enhanced Biphasic Rhodium Catalyst System

Platinum Co-ordination Compounds for Cancer Chemotherapy

Platinum Interlayers Improve Capacitor Performance

Platinum Metals Industrial Catalysts

The Fourth Grove Fuel Cell Symposium

Ruthenium-Cobalt Alloy Electrodeposition

Sixth Autocatalyst Plant Opens

Progress in Emission Control Technology

Fundamentals and Applications of Metal-Hydrogen Systems

Rhodium Express: ISSN 0869-7876

Doctoral Theses from the C.I.S.

Abstracts

New Patents

NO. 2

54

62

63

64

65

67

68

72

73

75

78

79

80

89

Communications should be addressed to The Editor, Susan V . Ashton. Platinum hleials Revietu

Jolinaon Mutthc? Public Limited Conipnri?. Hcttton Gccrdrn, London ECl LV 8EE

Osmium Bipyridyl Redox Polymers Used in Enzyme Electrodes By T. J. Ohara Department of Chemical Engineering, University of Texas at Austin, Austin, Texas, U.S.A.

A review of the background of biosensors which utilise osmium complexes for monitoring the glucose levels in diabetic patients is presented. A n electrochemical system, based on an osmium redox polymer, is described; the system is aimed at being a reliable, compact and miniature in vivo sensor for implantation into diabetic patients for continuous monitoring of their blood glucose levels. The sensor is about to begin trials on human volunteers.

Biosensors are extensively used in clinical diagnostic procedures (1-3). The research and development currently being undertaken in biosensors is aimed at achieving a faster response with more accurate results from smaller samples, so that analytes, such as glucose, lactate, enzymes and immunoproteins, can be monitored. The largest segment of the biosensor market is concerned with the care of diabetic patients.

It was reported recently that patients suffer- ing &om Type 1 diabetes who strictly controlled their diet and in addition measured their blood glucose levels four times a day experienced 60 per cent fewer diabetes-related complications, such as blindness, kidney failure, nerve damage, circulatory problems and heart disease (4). Type 1 diabetics produce very little of their own insulin and depend on insulin injections to regulate their glucose levels.

Unfortunately, most diabetics do not measure their blood sugar levels more than twice daily because of the cost, inconvenience and dis- comfort - such measurements require the with- drawal of blood and the injection of insulin. This suggests that there is a need for a miniature and easily implantable sensor which could moni- tor glucose intermittently or continuously, thus eliminating the need to withdraw blood. Such an intermittently or continuously operating glucose sensor could be coupled to a portable insulin pump through a microprocessor-controlled feedback loop (5). This would provide

better control of glucose levels by reducing the magnitude of fluctuations caused by diet or physical activity. Such a sensor would require miniaturisation and improvements to the existing stability, selectivity and biocompatibility.

Electrochemical Biosensors Electrochemical biosensors are now replacing

optical ones in commonly used applications because they are of relatively simple construction, inexpensive and can be easily miniaturised. They are quite sensitive to amperometric currents in the picoampere range or charges in the nanocoulomb range. The dynamic range of an electrochemical sensor can be made as wide as is needed for overlapping the medically relevant range. Another advantage is that they can sense samples in light absorbing or turbid solutions, such as whole blood.

The weddry optical test strips which are used for home glucose measurements in whole blood often require that the test strip be wiped or blot- ted with a tissue, so that the opaque blood sam- ple does not interfere with measuring the colour change. The reflectance colorimeter, into which part of the whole blood-treated test strip is inserted, becomes fouled by residual blood and thus requires periodic cleaning.

However, in electrochemical glucose measurements taken at home only the leads of the electrode need to contact the electronic measuring instrumentation. Thus, such assaying systems require less maintenance as residual

Platinum Metals Rev., 1995, 39, (2), 54-62 54

- 0 . 4 V .0.1 toQJV 4 2 t0o .4~ YE. SM.

$-0- Glucose

Gluconolacton

Ascor ba te

Acetaminophen

Fig. 1 Reaction cyclea of ‘‘electrically wired” glum oxidase, for an electrode coated with an osmium polymer complex and glucose onidase where the electrons released during the oxidation of glucose move via the o s m i ~ m complex to the electrode. Interferant oxidation pathways are also shown

whole blood is left on the test strip and cannot foul the instrument (6).

Enzymes are employed in most amperometric biosensors because of their high selectivity; ideally, it would be better to avoid enzymes because they are inherently unstable. However, man-made molecular recognition systems do not yet offer the selectivity and sensitivity which can be achieved with enzymes (7). There are some redox enzymes, including glucose oxidase (GOX), which cannot exchange electrons directly with electrodes because their redox active sites are buried deep inside a glycoprotein shell. Many enzymes have buried active sites in order to prevent the indiscriminate exchange of electrons with other redox proteins and to assure selectivity. Recent crystal structure studies of GOX have shown that the active site is approximately 15 A from the periphery of the enzyme (8Y9).

In order to transfer electrons between the redox active site and the electrodes, mediators (med) such as osmium bipyridyl complexes (lo), fer- ricyanide (1 1) , quinones (1 2), ferricinium derivatives (1 3, 14) and ruthenium complexes (1 5) are used, see following Equations (i) and (ii).

Glucose + GOX-FAD + Gluconolactone + GOX-FADH, (i)

GOX-FADH, + med(ox) + GOX-FAD + med(red) (ii)

GOX-FAD/GOX-FADH2 represents the oxidisedreduced states of the flavin active site of GOX. For in vivo sensing, where leaching of the mediator is not acceptable, the electrons must be relayed to the electrode from the enzyme through an immobilised electron relay. Electron relays of low molecular weight, which can dif- fuse freely, allow the indiscriminate exchange of electrons between the redox protein enzymes and also short circuit the essential electrochemical pathways necessary for life. The herbicide ParaquatTM (N,N’-dimethylviologen) is an example of a toxic electron relay that short circuits physiological redox systems.

Osmium Polymer Mediated B’ losensors

Osmium complexes, particularly bipyridines, terpyridines and phenanthrolines, have particularly high self-exchange rates - divalent and trivalent complexed osmium ions exchange

Platinum Metals Rev., 1995, 39, (2) 55

(a ) R(:unsubstitutcd 4: unsubstitutcd

(b) Rq=CHj R2= unwblti tuted

( c ) R$:CW2-CH~-COi Rz: CHz-CH2-COz-N b

0 ( d Ri: CHz- CHz-NHaCl

Rz= unsubstituted

Fig. 2 Chemical structure of osmium bipyridyl complexes eo- ordinated to partially quaternised poly(4-vinylpyridine) cl L> c> (left) or poly( 1-vinylimidazole) (right) i

( f ) RJ:CHj

electrons at high rates. We have therefore built reagentless sensors containing a redox enzyme and an osmium complexed polymer, where the polymer relayed electrons via the osmium centres between the enzymes and the electrodes. The osmium polymer electrically connects the redox centres of enzymes, such as GOX, by introducing electron relays close to the enzyme active site. The osmium redox sites serve as step- ping stones, allowing electrons to hop from the electron-rich active site of the reduced enzyme to the first osmium relay, from the first relay to a second relay, and so on until finally from a relay to the electrode.

These “wires”, which relay electrons, form electron conducting hydrogels upon crosslinking. The fluid (non-rigid) chains in these gels act to form electrostatic complexes between the enzyme molecules and their segments, and transfer electrons upon colliding with each other. The collisions shorten the path lengths that an electron must traverse on its way to an electrode. This path would be much longer ifthe electron proceeded exclusively along the tortuous route of a folded polymer chain.

Figure 1 shows schematically how a “wired” GOX sensor transduces the glucose concentration, that is flux, into an oxidation current. Electrodes such as gold, vitreous carbon, graphite, or M oxide can be modified with additions of the osmium redox hydrogel containing GOX. GOX serves as the selective biolog- ical component (hence the term biosensor), while the osmium redox polymer serves as the electron relay, shuttling electrons from GOX to electrodes. Glucose is oxidised to gluconolactone in the reactive centre of the GOX mole- cule, (Equation (i)) and in the process it reduces GOX-FAD to GOX-FADH,. Next, an osmiumm redox site in close proximity to the enzyme accepts an electron from GOX-FADH,, which effectively oxidises the enzyme back to its GOX- FAD state. The electrons associated with the osmium” redox site are shuttled via the redox polymer to the electrode through a series of self- exchange reactions, when the anode is held at a sufEciently positive potential. Ideally, the reactions occurring inside the film are very fast making the response time short, typically of a duration less than one second.

Platinum Metals Rev., 1995,39, (2) 56

The structures of some osmium redox polymers or “wires” which have been studied in our laboratory are shown in Figure 2. The backbone of the polymer usually consists of poly(4- vinylpyridine) (PVP) or poly( 1-vinylimidazole) (PVI), where some of the pyridine or imidazole groups are complexed with Os(bpy),Cl to form polymers termed PVP-Os, Figure 2(a), and PVI- Os, Figure 2(e), respectively (3, 10, 16-26).

PVP-0s is only slightly soluble in water except at high osmium loadings. However, when some of the remaining uncomplexed pyridine groups are quatemised with various side chains, the solubility of PVP-0s in water is enhanced. If the side chains also introduce amines, see Figure 2(d), PVP-0s then becomes easy to crosslink.

OH

R~ Fig. 3 (a) Chemical structure of A., the di-epoxide crosslinking agent, poly(ethy1ene glycol) diglycidyl ether, peg, n = 9 (b) reaction of an epoxide with

(c) reaction of an epoxide with

- , , - , H A ( b ) Rq-NH, +

7’ ( C ) 7’ L~+J N anamine

I R, imidazole

Earlier Osmium Polymer Mediated Glucose Electrodes

The first glucose electrodes mediated by osmium polymers were prepared in 1989 by Degani and Heller (1 7). They synthesised a water soluble cationic redox polymer consisting of PVP complexed with Os(bpy),Cl and partially N-methylated at some of the remaining uncomplexed pyridine groups, see Figure 2(b). The positively charged osmium polymer was adsorbed onto a graphite electrode by dip- coating in an osmium polymer solution. The electrode was then treated with the negatively charged GOX, forming an ionic complex.

In order to bind the members of the enzyme/polymer complex together covalently, diazonium salt derivatives of the polymer were reacted with tyrosine residues on GOX. This

was accomplished by the co-polymerisation of 4-aminostyrene with 4-vinylpyridine followed by treatment with sodium nitrite. The diazonium salt formed an azo linkage with the tyrosine groups on GOX. However, the resulting polymer/enzyme complex formed was a poorly crosslinked structure, due to their being few tyrosine residues on GOX.

The next osmium redox polymers used for enzyme electrodes were chosen so that they would react with the more abundant lysyl residues on GOX. This enabled crosslinked 3-dimensional polymer networks to be formed on the electrode. A PVP-based osmium polymer quaternised with the reactive propionic ester of N-hydroxy succinimide, see Figure 2(c), was synthesised by Gregg and colleagues ( 19). They constructed sensors by mixing the osmium redox polymer with GOX and tetraeth- ylenetetraamine to form rugged 3-dimensional crosslinked films. These films were unique in having both adequate electron diffusion coefficients and also in being permeable to water soluble substrates and products of enzymatic reactions.

However, the extent of the crosslinking formed by the reaction of the N-hydroxy succinimide ester and the enzyme amines was not reproducible, due to the N-hydroxy succinimide ester undergoing competing hydrolysis.

Subsequently, another PVP-based osmium polymer, derivatised with bromoethylamine, was synthesised, POs-EA, where EA represents ethylamine, see Figure 2(d), (10,20). The polymer was quaternised with ethylamine functions

Platinum Metah Rev., 1995, 39, (2) 57

Fig. 4 Schematic drawing of a four-layer recessed miniature implantable glucose electrode. 1: sensing layer; 2: insulating 7 layer; 3: interferant eliminating layer, which consists of horseradish peroxidase and lactate oxidase; 4: biocompatible layer of photocrosslinked tetraacry-

0-29mm

Polyimidc lated polyethylene oxide

to increase its water solubility, to allow for facile crosslinking and to promote favourable ionic interaction between the polymer and the enzyme. Pendant amine groups on the osmium redox polymer and on the lysyl residues of GOX were crosslinked with a commercially available long- chain water-soluble di-epoxide curing agent poly(ethy1ene glycol) diglycidyl ether (peg), see Figures 3(a) and 3(b).

Crosslinking POs-EA and GOX with peg formed reproducible hydrogels and resulted in enzyme electrodes that produced electro-oxidation currents proportional to glucose concentrations. The POs-EA-GOX-peg system is effective for “wiring” not only GOX, but also other enzymes, such as lactate oxidase (22,26), glycerophosphate oxidase (22), glucose dehydrogenase (25), horseradish peroxidase (24) glutamate oxidase (27), sarcosine oxidase (27) cellobiose oxidase (28), and many others.

Miniature Glucose Electrodes Implanted Subcutaneously

Glucose electrodes constructed with osmium redox polymers are easily miniaturised for in vivo use because they can carry high current densities. Typically miniature glucose electrodes with response times of less than 1 second have been reported, these being supported on a 7 p sized carbon fibre (2 1). Additionally, micro- electrodes with this construction have displayed a 10-fold increase in current density of 10.’ Ncm’ and a reduction in oxygen sensitivity has been observed (21).

These advantageous properties are caused by radial electron transfer through the osmium polymer on a microelectrode as compared with

planar electron transfer in the macroelectrode. For in vivo subcutaneous sensing, 290 p diameter GOX electrodes coated with osmium redox polymer have already been developed. These contain no components that can leach into the body and require no additional reagents. In order to provide selectivity, stability and

biocompatibility for our miniature implantable glucose electrode, we employed a four layer sandwich structure in a recessed gold electrode, see Figure 4, (29).

By using a recessed electrode, the sensing layer is protected from mechanical damage and the transport of glucose is reduced, which thus increases the linear range of the sensor. Ascorbate (vitamin C), urate, and acetaminophen (TylenolTM) and other interferants which are commonly found in serum can be non-selectively oxidised at the osmium redox sites and at the electrode, see Figure 1. In order to prevent such interference, the interferants were eliminated by oxidation in a crosslinked layer of horseradish peroxidase and lactate oxidase between the sensing layer and the body tissue (23).

Lactate and oxygen are also common components of serum, and the reaction between them is catalysed by lactate oxidase to produce pyruvate and hydrogen peroxide, see Equation (iii). The hydrogen peroxide which is generated oxidises the horseradish peroxidase which “bums up” the interfering hydrogen donors, HA, such as ascorbate, urate, and acetaminophen, see Equation (iv) . In this way the crosslinked layer of horserad-

ish peroxidase and lactate oxidase reactively eliminates the flux of interferants from both the


Fig. 5 Current output of two subcutaneously implanted sensors, tracking the blood glucose levels before, during and after an intraperitoneal infusion of glu- corn. The solid circles reprmnt the blood glucose levels measured on samples withdrawn from the tail vein of the rat using an independent glucose ~~

reference assay (Yellow Springs Instrument, YSI, glucose

(A) shows the output of the electrode implanted subcutaneously in the chest

O

2 5

2 2 0

aualyser). 2 15

Infusion stop

I R l t I awakes m I

Infusion start

I I!

I \ (B) represents the output of the electrode implanted subcutaneously in the intrascapular area of the rat

5 i 50 I50 2 5 0 350 450 !

TIME, rnin

400

350

300

250

- P

200 - u) >

150

100

50

0 1

osmium polymer “wired” sensing region and the electrode. Because lactate oxidase and horseradish peroxidase can themselves be “wired” with the osmium redox polymer, an insulating layer is placed between the osmium polymer and the interferant pre-oxidising layer.

lactate oxidase Lactate + 0, - Pyruvate + H,O, (iii)

horseradish peroxidase 2 HA + H,O, - 2A + 2H,O (iv)

The outermost layer of the in vzvo sensor, which contacts the body, consists of a biocompatible polymer layer (photocrosslinked tetra- acrylated polyethylene oxide) which prevents adsorption of protein (30).

Because these sensors are thus not affected by interferants, their output in the absence of glucose is nil, so that their calibration line passes through the origin. This means they require only a one point calibration in viva

In these sensors, at body temperature of 37”C, a glucose concentration change of 1 mM causes a change in the current of 3.5 nA. Current increases linearly with glucose concentration, up to a concentration of 20 mM. The sensors show only a ? 5 per cent variance in sensitivity

throughout 72 hours of being in continuous use. In vivo glucose monitoring with two electrodes

implanted subcutaneously in the thorax and between the scapulae of a rat, is shown in Figure 5. An electrocardiograph electrode was used as both counter and reference electrodes. Current was monitored before and after intraperitoneal glucose infusion for 1 hour. Glucose concentrations in the blood were determined periodi- cally from blood withdrawn from the tail using an independent reference assay. The glucose concentration correlated well with the current of the two subcutaneous sensors.

Increased Selectivity on Utilising a Polymer of Lower Redox Potential

In order to eliminate the necessity of a four layer sandwich electrode a simpler method was devised to reduce the level of oxidation of the interferants. An osmium polymer of sufficiently low redox potential which allows the sensor to operate at potentials where the oxidation of interferant is slow, both on the electrode and in the redox hydrogel of the sensing layer, has been used (31).

This low potential osmium redox polymer has a PVI backbone partially complexed to


5 io I 5 2 0 GLUCOSE CONCENTRATION, mM

Fig. 6 Dependence of the steady-state current density on glucose concentration in the presence of 50 pM ascorbate, 0.4 mM urate, and 1 mM acetaminophen and without interferants present: (a) no external membrane, with interferants (circles), without interferants (+); (b) Nafion membrane, with interferants (squares), without interferants (x). The flow cell operates at 1.4 ml/min in air

Os(dimethylbpy)&l, termed PVI,,-dme Os, see Figure 2(f). The electron donating methyl substituents on the bipyridyl rings shifted the redox potential of the polymer to 95 mV vs. S.C.E., which is 185 mV more reducing than POs-EA. At the operating potential of the resulting enzyme electrode, - 200 mV vs. S.C.E., the electric currents which result from the electro-oxidation of interferants are small in comparison to the glucose electro-oxidation current.

In contrast to the PVP-Os, the PVI,,-dmeOs polymers are already water soluble and do not require quaternisation with bromoethylamine. The uncomplexed imidazole groups can be easily crosslinked with water-soluble di-epoxides, see Figure 3(c). Since no ethylamine groups need to be added, the PVI,,-dmeOs is simpler to synthesise than POs-EA.

A steady-state flow cell calibration curve under air in the presence and absence of the interferants 0.4 mM urate, 50 pM ascorbate and 1 mM acetaminophen is shown in Figure 6, for an electrode prepared with a crosslinked layer of PVI,,-dmeOs and GOX. In order to extend the

linear range up to 30 m M of glucose, a layer of Nafion overcoating was employed. This layer limits the flux of the substrate.

The normal concentration ranges in human serum for urate and ascorbate are between 0.18 and 0.42 mM and 0.23 to 85 pM, respectively (32). The upper level for the acetaminophen concentration in human serum is between 0.1 to 0.2 mM when the maximum therapeutic dose of 1000 mg of acetaminophen is administered (33).

Thus the PVII5-dmeOs electrodes can measure glucose selectively in the presence of mul- tiple interferants. The Nafion coating did not increase the selectivity of the sensor, but served only as a mass-transfer limiting layer to increase the linear range of the sensor.

Dehydrogenase-Based Enzyme Electrode

There are several hundred dehydrogenase enzymes that use NAD(P)H, (coenzyme nicotinamide adenine dinucleotide phosphate, an electron acceptor for many dehydrogenases; its reduced form NAD(P)H donates electrons to the electron transport chain) which have been isolated, and with them it is possible to sense about a thousand substrates.

However, the oxidation of NAD(P)H by electrochemical techniques has proved to be difficult because it requires the concerted transfer of 2 electrons and a proton (34). NAD(P)H can be irreversibly oxidised at the electrode surface a t high overpotentials. There are however 2-electron mediators derived from phe- noxazines and phenazines that electrocatalyse the oxidation of NAD(P)H at low potentials (35-37).

A complex but nonetheless fast and efficient method for the detection of NAD(P)H has been developed by Vreeke and co-workers in our laboratory, and is shown in Figure 7. NAD(P)H was reacted with oxygen in a homogeneous 2-electron transfer reaction which was catalysed by the 5-methyl-phenazonium ion (PMS), to produce hydrogen peroxide and NAD(P)'. The hydrogen peroxide was then detected by its elec- troreduction to water with osmium polymer


0mVIS.C.E.) Fig. 7 Reaction cycles in NAD(P)H cathodes which could be used to detect a variety of sub- N*D(PIH

strates

NALXPI’

“wired” horseradish peroxidase. Thus the NAD(P)H concentration was measured as a reducing current.

Conclusion “Wired” enzyme biosensors have become a

useful analytical tool due to the simple con-

and are easily miniaturised, they can be implanted in the body for continuous in vivo monitoring of analytes, for example glucose. The technical hurdles involved with in vivo implantation are now being overcome and experimental use in human volunteers has begun.

based redox hydrogels, a wide array of o~doreductase enzymes has been uWireg and

enzyme electrodes require no additional reagents

of Professor Adam Heller during his research: This work was supported by the Office of Naval Research, the National Science Foundation, the National

the Robert A. Welch Foundation. several malpes can be assayed. Because ‘‘wired” Institute (grant 5 R 0 1 DK420 15-03, and

References

10

1 1

12

13

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“wired” horseradish peroxidase. Thus the NAD(P)H concentration was measured as a reducing current.

Conclusion “Wired” enzyme biosensors have become a

useful analytical tool due to the simple construction, fast response and feasibility for miniaturisation. Using crosslinked osmium polymer- based redox hydrogels, a wide array of oxidoreductase enzymes has been “wired” and several analytes can be assayed. Because “wired” enzyme electrodes require no additional reagents

and are easily miniaturised, they can be implanted in the body for continuous in vivo monitoring of analytes, for example glucose. The technical hurdles involved with in vivo implantation are now being overcome and experimental use in human volunteers has begun.

Acknowledgment The author gratefully acknowledges the support

of Professor Adam Heller during his research. This work was supported by the Office of Naval Research, the National Science Foundation, the National Institute of Health (grant 5 R01 DK42015-03), and the Robert A. Welch Foundation.

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Ligand- Enhanced Biphasic Heterogeneous catalysis has a distinct advan-

tage over catalysis in homogeneous media, in that the catalysts are easily separated from the products. Homogeneous systems with two liquid phases were developed for soluble catalysts in order to overcome this separation prob- lem, but the catalysed reaction relies on the transfer of organic substrates into an aqueous layer, and as a result the reaction rates are much lower than those for conventional homogeneous catalysis. Two-phase, or biphasic, catalysis is used commercially in the Ruhrchemie-RhBne Poulenc process for the hydroformylation of propylene to butyraldehyde using a water- soluble rhodium complex catalyst containing triphenylphosphine trisulphonate (TPPTS) .

This is an interesting variation of the hydroformylation process developed by Johnson MattheyIDavy McKee/Union Carbide in the 1970s, which uses a single phase organic reaction medium. In 1986, it was reported that 5.9 million tonnes of 0x0 alcohols were produced annually using homogeneous catalysis; the largest scale use of such catalysts.

However, work is now reported which high- lights an interesting and useful variation of the approaches that can be used in biphasic catalysis to improve the performance of the catalyst, (“Enhancement of Interfacial Catalysis in a Biphasic System Using Catalyst-Binding Ligands”, R. V. Chaudhari, B. M. Bhanage, R M. Deshpande and H. Delmas, Nature, 1995,

The authors describe research which shows that catalysis at the interface between phases in a biphasic aqueouslorganic system can be enhanced by using a ‘promoter ligand’. This lig- and is soluble in the organic phase and insoluble in the aqueous phase, but will bind to the water-soluble organometallic catalyst, thus func- tioning as an enabling agent. Using this technique, the catalyst concentration is increased at the interface between the phases and promotes

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Rhodium Catalyst System a significant enhancement in the reaction rate.

The ligand, which is in addition to those in the rhodium TPPTS catalyst, is insoluble in the aqueous (catalyst) phase, but has a strong affin- ity for the metal complex catalyst. Since the catalytic complex is insoluble in the organic medium, the reaction of the ligand, such as triphenylphosphine, with the [Rh(COD)Cl)],/ TPPTS (I) catalyst, (where COD is 1,5-cycZo- octadiene) will essentially occur at the liquid- liquid interface, and enhance the concentration of catalytic species there. Thus, they can access the reactants present in the organic phase in much higher concentrations than when the triphenylphosphine is not present. This can result in a dramatic increase in the rate of the biphasic catalytic reaction.

The authors demonstrate this new approach using the hydroformylation of 1-octene in the presence of the rhodium catalyst system (I). Here the hydroformylation proceeds at a turnover frequency in the range 10 to 50 times faster when triphenylphosphine is added.

Recent work described here and elsewhere indicates that modifications of the homogeneous technique could increase and broaden its potential. Papers which support this view include one by K. T. Wan and M. E. Davis (Nuture, 1994, 370, (6489), 449-450) (with comments by J. M. Brown and S. G. Davies (ibid., 418-419)) where heterogeneous analogues of homogeneous catalysts are reported, involving interfacial transfer and a catalyst supported on glass micro- beads. The potential for high enantiomeric excess in stereospecifc synthesis is demonstrated by combining advantages of homogeneous and heterogeneous catalyst systems. These papers are an important development from earlier work on phase transfer catalysis, and with the new approaches are likely to lead in due course to more commercial applications for soluble catalyst systems based upon the platinum group metals. D.T.T.


Platinum Co-ordination Compounds -

for Cancer Chemotherapy A new feature of the Seventh International

Symposium in the series on Metal Co-ordination Compounds in Cancer Chemotherapy, held in Amsterdam from 1st to 4th March, 1995, was the presentation of the Barnett Rosenberg award for contribution to the field of platinum- based chemotherapy. The recipient of the award, Professor Ken Harrap of the Institute of Cancer Research, London, described to the audience the history of the development of cisplatin and carboplatin and the selection of JM-216 as a candidate for an orally administered agent. He concluded by reporting ongoing work aimed at identifying compounds capable of extending the application of platinum chemotherapy by over- coming the resistance seen to cisplatin and carboplatin. In particular he highlighted the potential of tram compounds, an area which was raised in a number of other presentations on novel compounds.

In presentations on clinical experience with the newer platinum analogues, JM-216 was

shown to have myelosuppression as its dose limiting toxicity in a daily x 5 schedule, and it has now entered Phase I1 trials in Europe for the treatment of lung cancer. Oxaliplatin, an analogue which has been in trials for some time now, was shown to offer benefit in colorectal cancer when combined with other drugs and using chronomodulated delivery. Lobaplatin continues to be evaluated in Phase I1 trials in Europe. In Japan, approval has been sought for the marketing of 2 5 4 4 which has shown activity in the treatment of head and neck and gas- tro-intestinal tumours, and a new second generation analogue, TRK-7 10, has entered Phase I testing.

A debate on the relative merits of cisplatin and carboplatin in the clinic concluded it was clear that carboplatin was preferred in a palliative set- ting and in high dose treatments. In testicular and good-prognosis ovarian cancer patients, where cisplatin drug combinations are known to produce a high percentage of cures,

0 w 0

JM-216 Oxalipratin Lobaplatin

254-5 TRK-710


concern regarding the therapeutic equivalence of carboplatin limits its use as an alternative. The different toxicities of the two drugs give each advantages in particular combinations for specific treatments, and in this context it was noted in several presentations that the combination of carboplatin and paclitaxel (taxol) is showing promise in ovarian and lung cancers. Confirmation of these early results by more definitive studies is eagerly awaited.

Much research is now being devoted to the understanding of cellular control mechanisms

involved in cell proliferation and cell death. While it was initially proposed that chemotherapeutic agents capable of influencing these mechanisms might replace the use of cytotoxic therapy, presentations at this symposium suggested that it is more likely that they will be used in combination with cytotoxic compounds, such as the platinum drugs, to increase their effectiveness. It seems likely therefore that the platinum drugs will remain a vital part of cancer chemotherapy and a topic of international interest for some time to come. C.F.J.B.

Platinum Interlayers Improve Capacitor Performance The small non-volatile ferroelectric capacitors

used in commercial memory devices need to have low leakage currents, to prevent charge loss and early breakdown of the device, and to have acceptable dielectric breakdown properties. Capacitors used in such devices must also be able to withstand, without breaking down, the repeated in use switching that is typical for such devices.

Thin film lead zirconate titanate (PZT) capacitors, when grown on oxide electrodes, such as those of ruthenium or lanthanum strontium cobalt, have excellent resistance to the loss of polarisation that occurs upon repeated switching; indeed PZT films grown on ruthenium oxide specifically by the sol-gel process are free of polarisation fatigue for up to 1O”cycles.

However, capacitors produced in this way have high leakage currents and inconsistent properties. Nevertheless, it is suggested that if these problems were overcome, these capacitors could be used successfully in non-volatile ferroelectric memory devices.

Researchers from North Carolina State University and MCNC Electronics Technology Division, North Carolina, have now produced capacitors with reduced leakage and smaller property variations by introducing a thin interlayer of platinum on the ruthenium oxide electrode (H. N. Al-Shareef, K. R. Bellur, A. I. Kingon and 0. Auciello, “Muence of Platinum Interlayers on the Electrical Properties of RuOz/Pb(Zro 53Tio47)03/Ru02 Capacitor Heterostructures”, Appl. Phys. Lett. , 1995,66,

Capacitors were fabricated by first depositing the lower ruthenium oxide electrode onto single crystal magnesium oxide by ion beam sputtering, followed ey the deposition of a platinum layer, about 100 A thick, on top of the electrode

(2), 239-241).

either by ion beam- or magnetron sputter depo; sition. The PZT thin film of thickness 2400 A was then deposited using a spin-on sol-gel process, followed by annealing. The upper ruthenium oxide electrode was deposited by ion beam sputtering and patterned using positive photo- lithography, followed by ion beam etching by argon ions.

The variations in the properties are caused because the films that are grown on ruthenium oxide are non-uniform and inhomogeneous, due to the presence of second phases. The high current leakage may be the result of a conductive pyrochlore-type second phase. In contrast, films that are grown on platinum are single phase, uniform and homogeneous, due to the easier nucleation of perovskite PZT on platinum than on ruthenium oxide electrodes.

The leakage current in capacitors with a platinum interlayer was reduced by two to four orders of magnitude, which made them more reliable, while still retaining the excellent resistance to fatigue typical of the unmodified capacitors. The difference between switched and non-switched polarisation for capacitors with the platinum interlayer was of the order of 50 pC/cmZ, which remained constant for up to 10” cycles. The effective resistivities of capacitors with magnetron- and ion beam sputter- deposited platinum films were about 5 x 1 O9 and 5 x 10” R cm, respectively, compared to values for capacitors without the platinum film of lo6 to 107R cm. The remanent polarisation values deviated by only 3 to 4 per cent for capacitors containing the platinum interlayer compared to about 20 per cent for capacitors without the platinum interlayer.

The best results were obtained when the platinum interlayer was deposited at an elevated temperature, rather than at room temperature.


Platinum Metals Industrial Catalysts Catalysis of Organic Reactions EDITED BY M. G. SCAROS AND M. L. PRUNIER, Marcel Dekker, New York, 1995, 599 pages, ISBN 0-8247-9364-1, U.S. $195.00

This book comprises a set of papers presented at the 15th Conference on Catalysis of Organic Reactions, held in Phoenix, Arizona, in May 1994. It covers a variety of topics, such as heterogeneous catalysis, asymmetric hydrogenation, hydrogenation, oxidation, hydroformylation, catalyst design and catalyst characterisation. One topic which is emphasised is hydrogenation (alpha to omega), and this is intended to allow a better understanding of the entire process, from choosing a catalyst to the noble metal “loop”. There are over 60 papers and 186 contributors, with a healthy number of these being from industry. A large proportion of the papers deal with reactions involving platinum group metal catalysts, reflecting their importance to both academia and industry.

The initial paper, by R. J. McNair from Johnson Matthey, provides an overview of the process of catalyst selection for heterogeneous platinum group metal catalysts in a new hydrogenation process. It includes discussion on the reasons behind the choices of catalytic metal, catalyst support, reactor design, catalyst design, catalyst separation, and spent catalyst recovery and refining. There is a description of the influence of catalyst preparation methodology on the selectivity of supported metal catalysts, exemplified by the hydrogenation of phenyl- acetylene using 5 per cent palladium on carbon. Other topics that are dealt with include the effect of the preparative method on metal dispersion, distribution and level of reduction and how each can affect the catalyst performance and, in particular, its selectivity.

The effect of reaction conditions on catalyst selectivity is then discussed by F. P. Daly and colleagues from Degussa, with reference to the hydrogenation of oximes and unsaturated C 18 acids using supported platinum group metal catalysts. Several factors, such as temperature, pressure, catalyst loading level, solvent system,

reactant purity, agitation and poisons are considered. This is followed by a paper detail- ing noble metal recovery operations and the various steps involved in the noble metal “loop”.

Heterogeneous catalysis in organic synthesis is discussed by R. L. Augustine and colleagues from Seton Hall University, New Jersey. This is illustrated by the platinum catalysed oxidation of alcohols, carbon-carbon bond forming reactions of supported palladium catalysts for the Heck type arylation of allylic groups, and by enantioselective heterogeneous catalysis, which includes the hydrogenation of a-ketoesters to chiral a-hydroxyesters using chinchona alkaloid modified platinum catalysts.

A detailed study of the homogeneously palladium catalysed coupling of aryl halides and aryl triflates to itaconate diesters is discussed by M. G. Scaros and co-workers from G. D. Searle and Monsanto. This can provide a convenient route to the intermediate E-benzylidene succi- nate diesters, which in turn can be hydrogenated to chiral R-benzylsuccinates with a high degree of optical purity, using rhodium-dipamp complexes as catalysts. In the coupling reactions aryl iodides were more effective than aryl bromides, and the nature of the itaconate diester did not appear to affect the efficiency of the reaction: aryl triflates were more sensitive to the reaction conditions than the aryl halides were.

The DuPont process for the direct combination of hydrogen and oxygen to form hydrogen peroxide is described in a contribution by J. R. Kosak from E. I. DuPont de Nemours. Some of the problems that are associated with the traditional anthraquinone process, such as consecutive hydrogenation and oxidation steps, and also aqueous-organic extractions have been overcome. It has been shown that doping a supported palladium powder with platinum has a synergistic effect, and this has resulted in an improved yield and selectivity to hydrogen

Platinum Metals Rev., 1995, 39, (2 ) , 65-67 65

peroxide. The attachment of this catalyst to a stainless steel mesh using washcoating techniques has avoided some of the drawbacks of a slurry cataly.t system and has provided an efficient means for directly combining hydrogen and oxygen.

The synthesis of primary amines from olefins, syngas and ammonia is dealt with by J. F. Knifton from Texaco Chemical Company and by J. J. Lin from Shell Development Company. This oxoamination reaction has been extended to butenes and homogeneous cobalt, ruthenium and rhodium systems have all proved effective, with ruthenium being the most productive.

Asymmetric Catalysis Several chapters then deal with the topic of

asymmetric synthesis. There has been particular interest in this as chiral molecules have become indispensable in the life sciences where there is a drive towards more active, specific drugs which do not have the undesired side effects that are associated with the presence of unwanted isomers. Ruthenium-BINAP complexes have become a popular catalyst system to study, since they have been shown to be effective with a range of substrates. S. Akutagawa from Takasago International Corporation, dis- cusses this area, with reference to the hydrogenation of aliphatic ketones, a-substituted P- ketoesters, and also the practical application of this technology towards the synthesis of Vitamin E, p-lactam intermediates and biodegradable polymers.

Further chapters deal with the use of ruthenium-BINAP systems for the hydrogenation of unsaturated carboxylic acids and with multi- nuclear NMR observations on the nature of the catalyst in the reduction of ketoesters.

The homogeneous hydrogenation of imines is discussed by B. R. James from the University of British Columbia, who describes work on asym- memc imine hydrogenation with rhodium phosphine catalysts, and by P. A. Chaloner and colleagues from the University of Sussex who describe the reduction of PhN=CHPh using iridium phosphine complexes.

J. L. Margitfalvi, from the Central Research Institute for Chemistry of the Hungarian

Academy of Sciences, and R. A. Sheldon and co-workers from Delft University of Technology and the Technical University of Budapest, respectively, revisit the topic of heterogeneous asymmetric hydrogenation catalysts. In the paper by Sheldon the influence of alkaloid-type chiral auxiliaries on the hydrogenation of carbonyl and olefinic groups by supported palladium and platinum catalysts is described, and shows that the highest enantioselectivities, comparable with the previously reported chinchonidine, were obtained with the vinca-type alkaloid vinpocetinm.

The theme of the application of catalysis to the life sciences is continued by D. Forster and co-workers !?om Monsanto and Searle Discovery Research, who have used homogeneous catalysis including hydroformylation with rhodium, reductive amination with ruthenium, and hydrosilylation with rhodium-phosphines, for reactions on template polymers which can result in the synthesis of tailored polymeric drug delivery systems.

Some catalytic problems relating to rapid deac- tivation and scale up during the reductive amination of aldehydes and ketones, using palladium or platinum on carbon catalysts, are described by J. J. Birtill from ICI. This is followed by a paper from R. E. Malz and colleagues of Uniroyal Chemical Company and Georgetown Medical School, on the reductive alkylation of acetophenone with aniline. They show that bisulphided catalysts are more effective than their unsulphided counterparts and that a 3 per cent PtS, on carbon catalyst is supe- rior to sulphided rhodium, ruthenium, nickel or palladium systems for that reaction.

The influence of the medium on the nickel catalysed hydrogenation of 2-methyl glutaro- nitrile is described by G. Cordier from RhBne- Poulenc. In this reaction subsequent dehydrogenation of the intermediate by a catalyst of palladidsilica in a fixed bed configuration gave the desired product, P-picoline, in high yield. A paper by D. G. Blackmond and A. Waghray from the University of Pittsburgh, demonstrates the role that alkali promoters can play in hydrogenation. During the hydrogenation of 3-methyl

Platinum Metals REV., 1995, 39, ( 2 ) 66

2-butenal, catalysed by ruthenium/silica, the addition of potassium results in a shift in selectivity towards the unsaturated alcohol, provided that the potassium is in close proximity to the ruthenium.

Further examples of the influence of promoters in hydrogenations are given in other papers. These include rhodium-tin on silica catalysts, which give high selectivities to crotyl alcohol in the hydrogenation of crotonaldehyde; the selective hydrogenation of carboxylic acids to alcohols by sol-gel ruthenium-tin catalysts; the hydrogenation of bisphenol A using lithium hydroxide as a modifier, and the influence of alloying elements on the selectivity of platinum catalysts in the hydrogenation of phenol. Other topics that are discussed in both papers and/or posters include the influences of the support and the effect of the metal particle size on a variety of reactions catalysed by the platinum group metals.

Investigations by G. Centi and G. Stella from the Department of Industrial Chemistry and Materials, Bologna, on the selective oxidation of 1-butene to 2-butanone on solid Wacker-type catalyst systems comprising palladium supported on oxides, such as vanadium oxide, concluded that the main factors affecting catalyst performance are: the low desorption rate of products and the progressive reduction of vanadium oxide to strongly adsorbed species which inhibit reoxidation.

Catalytic oxidations with air for the clean and

selective transformations of polyols are described by P. Gallezot and colleagues from the Institut de Recherches sur la Catalyse-CNRS. In particular they discuss the oxidation of glyoxal to glyoxylic acids using platinum on carbon, and the conversion of glucose to gluconic acid using a palladium on carbon catalyst impregnated with bismuth. The latter catalyst system possesses some advantages over the commercial enzymatic process in that the reaction is carried out in one step in a single vessel with high yield per catalyst weight.

Papers by G. G. Stanley from Louisiana State University, on the uses of homobimetallic co- operativity with cationic rhodium catalysts are illustrated by the enantioselective hydroformylation of vinyl acetate to give intermediates in the production of L-threonine with enantiomeric excesses of 85 per cent. This is followed by a contribution by S. Wieland and I? Panster from Degussa, on the immobilisation of noble metal complexes and heterogeneous catalysts on polysiloxane supports and their application in organic synthesis.

This volume contains a large number of contributions by experts in various fields of catalysis and as such provides a wealth of information on a wide range of aspects of catalysis. By its very nature the information within the book is somewhat fragmented, and it is difficult to find related themes which recur in the text. Apart from this, it is a useful addition to the bookshelf for those involved in catalysis. M.J.H.R.

Following the pattern of the three earlier highly successful symposia, the fourth meeting will be held at the Commonwealth Institute, London, England, from 19th to 22nd September, 1995. This fuel cell symposium is being organised by a steering com- mittee composed of leading fuel cell scien- tists from both academia and industry, under the aegis of Elsevier Advanced Technology.

With the increasing interest in the efficient production of electricity combined with the introduction of legislation promoting ultra- low and zero emission vehicles, the potential market for fuel cell systems continues to grow. Internationally invited speakers, all world

The Fourth Grove Fuel Cell Symposium authorities on fuel cell technology and exploitation, will provide an up-to-date analysis of technical developments and the oppor- tunities for commercialisation of fuel cells; their contributions have been chosen to provide attendees with a complete picture of the progress achieved and the future prospects for fuel cell technology.

Those who would like to make poster presentations or who require further information about this symposium should contact Sharron Emsley, Fourth Grove Fuel Cell Symposium, Elsevier Advanced Technology, PO Box 150, Kidlington, Oxford OX5 lAS, U.K. Fax: +44(0) 1865 843971.

Platinum Metals Rev., 1995, 39, ( 2 ) 67

Ruthenium= Cobalt Alloy Electrode position By P. Juzikis, L. Gudaviciute and E. Matulionis Institute of Chemistry, Vilnius, Lithuania

Since little has been written about ruthenium alloy plating, the present work sets out to provide data o n the electrodeposition of ruthenium-cobalt alloys, using a sulphate-sulphamate electrolyte. Some operating conditions have been obtained for the production of thin crack-free coatings of ruthenium-cobult alloys.

There have been many developments in the electrodeposition of the platinum group metal alloys, platinum-cobalt and palladium-cobalt, which possess both perpendicular anisotropy and high coercive force, and are therefore being considered for a number of magneto-optic applications (1, 2). Recently a ternary alloy, platinum-ruthenium-cobalt, has been proposed for use as a magneto-optical recording medium (3). Ruthenium-cobalt alloys may also possess similar magnetic properties, but as yet there is no available data on this, and also there is no data in the literature on the electrodeposition of ruthenium-cobalt alloys. However, in the patent literature a process for alloying ruthenium with cobalt has been described, enabling ruthenium coatings containing several per cent of cobalt to be produced (4).

The present work therefore has been performed in order to obtain more information on

the electrodeposition of ruthenium-cobalt alloys from a sulphate-sulphamate electrolyte, and to establish some conditions for the process.

Experimental Procedure The electrolyte used for ruthenium plating was

prepared from ruthenium(IV) hydroxychloride Ru(OH)Cl, and cobalt(I1) sulphate-heptahy- drate. The pH of the electrolyte was adjusted by adding either 20 per cent sodium hydroxide solution or dilute (1 : 1) sulphuric acid. The contents of the standard electrolyte used were, in moH: -0.08 ruthenium(W), - 1.5 cobalt(II), - 0.35 sulphuric acid and - 0.4 sulphamic acid. The pH was 1.7. The electrolytes from which ruthenium and cobalt were separately deposited contained similar amounts of all the components, except that cobalt(I1) or ruthenium(IV) were excluded, respectively.

Current density and potential measurements

n

E a

5

60.03

*- z g0.02

c z W

50.01 u

2 3 1

Est POTENTIAL, V

Fig. 1 Linear sweep voltammograms for deposition of: 1: ruthenium from a standard electrolyte not containing cobalt; 2: cobalt from a standard electrolyte not containing ruthc- ninm; 3: ruthenium-cobalt alloy. All curves were obtained at a sweep rate of 1 mVls

Platinum Metals Rev., 1995,39, (2), 68-71 68

were carried out at a temperature of 60 k 0.5”C in air. The platinum electrode, of area 1 cm2, was activated in 10 per cent sulphuric acid before each experiment and kept for 5 minutes in the electrolyte before the start of the experiment. The potentials are given versus a normal hydrogen electrode. A platinum plate of area 6 cm2 served as the anode. Current efficiencies defined, according to Faraday’s Law, as the weight of material deposited compared to that required theoretically, expressed as a percentage, were determined by the gravimetric method, taking into account alloy compositions which were determined by an X-ray electronic micro- analyser. Partial curves were calculated from current efficiencies and alloy composition data, and were obtained under the potentiostatic conditions of the electrolysis.

Results and Discussions The current density/potential studies show

that there is no actual deposition of ruthenium or cobalt either separately or as an alloy within the potential range from the start-up potential, E,,, to 0 V, see Figure 1. When the pH of the electrolyte is 1.5 to 1.8, deposition of both metals begins at the same potential. When the pH is decreased the voltammograms for the separate depositions of ruthenium and cobalt shift to the region of less negative potential, the shift in the ruthenium voltammogram being the more significant. As can be seen in Figure 1 , code- position of both metals occurs with substantial polarisation at values of potential up to - 0.35 V, but with depolarisation at potentials more negative than - 0.4 V. The section of the ruthenium voltammograms at potentials ranging from - 0.25 V to - 0.4 V may be considered as corresponding to the limiting current, since a drop in the current efficiency for ruthenium electrodeposition was detected on increasing the current density, i,, further. The same section of the cobalt curve cannot be taken to be the limiting current of cobalt, since the current efficiency increases with a further increase in current density. It has been found that the current efficiency of cobalt is 75 per cent at values for the current density of 0.0 1 A/cm2 and is

0.07.

n

5

POTENTIAL, V

Fig. 2 Potentiostatic voltammograms for the standard electrolyte: 1: ruthenium-cobalt alloy deposition. Calculated partial curves: 2: cobalt deposition; 3: for deposition of ruthenium

95 per cent over the range of current density from 0.015 to 0.05 Ncm’. This results in a con- siderable redistribution of the partial current densities of cobalt and ruthenium when inaeas- ing the current density, i,, see Figure 2.

It should be noted that it is not possible to cal- culate the curve for hydrogen evolution from the data in Figure 2 due to the partial reduction of the ruthenium(1V) ions to lower oxidation states, namely ruthenium(II1) and ruthenium(II), which occur on the cathode at the same time as the deposition of ruthenium and cobalt, and the evolution of hydrogen (5).

The results of these investigations show that it is possible to deposit ruthenium-cobalt alloy from a sulphate-sulphamate electrolyte. It can be seen from the data in Figure 3 that the composition of the alloy is greatly dependent on current density, &. This indicates that there is a possibility of obtaining modulated coatings of ruthenium-cobalt alloys by pulse-plating (6-8).

The dependence of the amount of cobalt in the ruthenium-cobalt alloy on the current density is not as great when the pH of the electrolyte is decreased to 1.0, see Figure 3. In Figure 4 the current efficiency of the alloy deposition is


Fig. 3 Dependence of the cobalt content in the alloy on the current density, i,, at various pH values of the standard electrolyte

I

0 0.025 0.050 0.075 CURRENT DENSITY, i C , AIcrnz

shown to depend on the current density at different values of pH. By comparing Figures 3 and 4 it can be seen that the current efficiency is always higher when an alloy with high cobalt content is deposited. The current efficiency also decreases slightly with increasing temperature. This unexpected dependence is also apparent when the results shown in Figure 5 are examined; they show that the cobalt content in the alloy decreases when temperature is increased.

Experimental data therefore show that it is

5 001 003 005 007 009 CURRENT DENSITY i C , A l c m 2

4 0 50 60 70 TEMPERATURE, .C

Fig. 4 Dependence of the current efficiency of the alloy deposition on: current density, i,, in a standard electrolyte 1: at pH 1.0; 2: at pH 1.4; 3: at pH 1.7; and on: temperature, at i, = 0.02 Alcm’ 4: standard electrolyte at pH 1.7

possible to electrodeposit ruthenium-cobalt alloys containing different amounts of ruthenium and cobalt from a sulphate-sulphamate electrolyte. The composition of the alloy is determined by the pH of the electrolyte and by the value of the current density rather than by the ratio of metals in the electrolyte. The optimum composition of the electrolyte is, in mol/l: - 0.05 to 0.1 ruthenium(IV), - 1.0 to 1.5 cobalt(II), - 0.3 to 0.5 sulphuric acid, - 0.3 to 0.5 sulphamic acid and the pH of the electrolyte should be 1.2 to 2.0.

Semi-bright microcrystalline coatings, up to 2 pm thick, were obtained without cracks at deposition current densities ranging from 0.005 to 0.1 A/cm2. In Figure 6 micrographs of the surface of ruthenium-cobalt alloy coatings are shown. It can be seen that the smoothest coatings are obtained at a current density of 0.01 Ncm’, Figure 6(b). The size of crystallites is 0.03 pm. However, the coatings are not as smooth when they contain 85 per cent ruthenium and the current density is low. Coatings obtained at a current density of 0.015 A/cm2, Figure 6(c), (and which contain only 10 to 15 per cent of ruthenium) typically have a similar surface structure. No sharp shaped crystallites or their aggregates were found; in fact, both the crystallites and the aggregates had a round (domed) shape.

Preliminary investigations of the magnetic properties of the ruthenium-cobalt coatings


show that the coercive force of films containing 40 to 60 atomic per cent of cobalt was about 300 Oe. The coercive force increased to 500 Oe when the films were deposited by pulse plating.

As has been noted earlier, ruthenium(IV) ions are partially reduced at the cathode. This produces some variations in the results when measuring current efficiency and alloy composition. To achieve maximum reproducibility the prepared electrolyte should be kept for not less than 3 days, then used at the operating current density for some hours, at about 2 AhA. Under these conditions the variation in the current efficiency and alloy compositions did not exceed 10 per cent. In order to prolong the life of the bath the electrodeposition should be carried out in an apparatus with separate anode and cathode com- partments. The quality of the coatings in this case does not change after utilisation of 30 Ah/l of electrolyte. Depending upon the concentration of ruthenium(IV) ions, the electrolyte was adjusted by adding a ruthenium concentrate not containing sulphamic acid. A solution of sulphuric and sulphamic acids, both having a concentration of 0.4 mol/l, was used as the anolyte. In conclusion, ruthenium-cobalt alloys con-

taining 10 to 85 per cent of cobalt were obtained Fig. 6 Micrographs of the surfaee of ruthenium-cobalt alloy deposits obtained in standard electrolyte for current densities, in A/cm':(a) 0.005; (b) 0.01; ( c ) 0.015

4 0 50 60 7 0 TEMPERATURE, *C --

0.5 1 1'5

Fig. 5 Dependence of the cobalt content in the alloy on: 1: temperature, at & = 0.02 ~/crn*; 2: cobalt concentration in the standard electrolyte at i, = 0.01 A/cm2; 3: cobalt concentration in the standard electrolyte at i, = 0.05 A/cm*

COBALT CONCENTRATION. mOlll

from sulphate-sulphamate electrolyte. Crack- free semi-bright microcrystalline coatings, of thickness up to 2 p, were obtained. The coercive force of the films reached up to 500 Oe. The electrolyte remained stable, even after utilisation at 30 Ah/l.

References 1

2

3 European Patent Appl. 576,294A 4 US. Patent 4,375,392; 1983 5 P. Juzikis and L. Gudaviciute, Chemija (Vilnius),

1994, (3), 50 6 A. R. Despic and T. J. Tirsovic, 3. Appl.

Electrochem., 1993, 23, 662 7 European Patent 267,972 B1; 1993 8 P. Leisner, P. Moller and L. Alting, Galvanotechnik,

1991,82, (5), 1548

M. E. Baumgartner, Ch. J. Raub, P. Cavalotti and G. Turilli, MetaZlobetfZuche, 1987, 41, (1 l), 1559 R. Gontarz, L. Smardz, B. Szymanski and P. Juzikis,J Magn. Map. Muter., 1993,120,278


Sixth Autocatalyst Plant Opens JOHNSON MATTHEY COMMENCES PRODUCTION IN MEXICO

Mexican Government legislation has required the use of catalytic converters on all light duty vehicles from 1993 onwards. Clearly this will enable the platinum metals to make a further positive contribution to air quality, particularly in congested metropolitan areas.

Since that time domestic vehicle production in Mexico has grown to almost one million units annually. Despite recent economic difiiculties, the long-term fiture for the Mexican automobile industry remains bright.

In response to this situation, the Johnson Matthey Catalytic Systems Division opened its most recent autocatalyst plant in Queretaro, Mexico, and production commenced in January 1995. The facility is situated in the beautiful “Bajio” region of central Mexico, approximately 120 miles northwest of Mexico City. Located in the Bernard0 Quintana Industrial Park, the 3,500 square metres facility is situated among a variety of other automobile component suppliers, notably TRW, Rockwell, American Racing and Ford Climate Systems.

The new Johnson Matthey plant has a capacity of 1.5 million units per year, with approximately 50 per cent of the initial output being scheduled for fitting to vehicles intended for export to the United States of America.

The facility incorporates state-of-the- art flexible manufacturing technology and an advanced distribution process control system is used in the application of washcoat and noble metal materials. The manufacturing capability incorporates some of the most recent technological advances, and provides room for output expansion.

The official plant inauguration will take place on April 28th, 1995, when the Chairman of Johnson Matthey, David Davies, will be host to the Governor of the State of Queretaro and the British Ambassador to Mexico, together with honoured guests from seven major vehicle producers. J.B.F.

Plarinum Metals Rev., 1995, 39, (2), 72 72

Progress in Emission Control Technology A SELECTIVE REPORT OF THE SAE DETROIT MEETING

Traditionally, the Congress of the Society of Automotive Engineers (SAE), held each year at the end of February in Detroit, U.S.A., has been the magnet for people involved in all aspects of automotive engineering, including those concerned with emission control. The 1995 meeting, held from 27th February to 2nd March, will be the last occasion when emissions feature as part of the programme at the main Congress. Instead, in 1996, this topic will form a major part of two separate meetings to be held under the aegis of the Fuels and Lubricants Activity in the Spring and in the Autumn.

Nevertheless, at the Congress this year, there were a number of papers devoted to the control of emissions from both gasoline and diesel fuelled engines. Interest was focused principally on systems meeting the tightened legislative requirements appertaining to the U.S.A. and Europe between now and the year 2000.

This review can cover only a proportion of the papers presented, but they have been selected to show the principal trends in the ongoing developments of this area of technology.

Palladium-Based Three-Way Catalysts

There is a strong continuing development of new three-way catalysts based on palladium, either alone or in combination with rhodium and platinum. The excellent low-temperature performance and high-temperature resistance of palladium, coupled with its ability to reduce hydrocarbon species in the exhaust gas, make it an important component in systems designed for future U.S. and European applications. This was illustrated in a paper by Z. H u and R. M. Heck (Engelhard) who described the performance of close-coupled palladium catalysts stabilised with base metal promoters on a vehicle in the FTP (Federal Test Procedure) test cycle, after extended ageing for 24 hours in air at temperatures up to 1050°C. The precise formula- tion of palladium-containing systems can depend

on a number of factors, including performance requirements and fuel quality considerations. For example, previous studies have shown that the conversion performance for nitrogen oxides by palladium-only catalysts is more susceptible to poisons in the exhaust gas (fuel-derived sulphur and lead species) than is the conversion activity for hydrocarbon and carbon monoxide.

Rhodium is the metal normally used to enhance nitrogen oxides performance in auto- catalysis, and R. J. Brisley, G. R. Chandler and colleagues (Johnson Matthey) described the development of a number of advanced palladium-containing formulations, based on opti- misation of beneficial interactions of the noble metal and washcoat components. The authors found that palladium-rhodium formulations made in this way were particularly suited to close-coupled applications in markets where the availability of unleaded fuel is good, and where any trace lead levels are low (as in, for example, the U.K. and Germany). However, incorporation of some platinum to give a p1atinum:pal- 1adium:rhodium trimetal combination gives improved lead tolerance, and may be preferred - especially in cooler, underfloor locations - where the possibility of poisoning by residual lead exists.

A further advantage of the advanced high-palladium content catalysts is that they generate less hydrogen sulphide under rich conditions. Many current catalyst-equipped vehicles contain more than one catalyst unit, and benefits can sometimes be obtained by having different formulations on each brick. However, the same authors show that the balance of oxidants and reductants passing through each catalyst unit needs to be carefuuy considered if optimum performance of the complete system is to be obtained.

The advantages of adding rhodium and platinum to palladium in catalysts for European applications were also described by A. Punke, U. Dahle and colleagues (Engelhard), who


showed that optimised trimetal formulations gave a better performance than either palladium- only catalysts, or the platinum-rhodium catalysts that are currently in use.

Cold Start Hydrocarbons Emission Control

The debate continues on the best means to control hydrocarbon emissions in the period before the main catalyst becomes fully opera- tional, with a number of options still being considered. One possibility is to lower the light- off temperature of the catalyst itself. Advances in this area were reported by S. E. Golunski, H. A. Hatcher and colleagues aohnson Matthey). Newly developed platindceria-palladium technology offers substantially improved steady-state and dynamic light-off performance, compared to the palladium-only system. By combining this technology with low thermal mass substrates, and by utilising stoichiometric or lean cold start engine calibration strategies, the improved low-temperature performance of the new catalyst can be exploited.

Of the alternative ways to attack cold start emissions, a number of papers discussed electrically heated catalyst (EHC) technology, including ones fi-om Corning, Grace, and a team from the German automobile manufacturers. It is clear that EHC based systems when used together with conventional catalysts are capable of meeting stringent legislative limits. However, the main concern remains the trade- off between electrical power and performance, and how that power should be generated.

Diesel and Lean Burn Engines Emphasis on pollutant control from lean burn

engines, whether diesel or gasoline, has focused on the removal of nitrogen oxides since the other principal pollutants, hydrocarbon and carbon monoxide, are normally easily removed under lean conditions. Nevertheless the catalytic converter on a diesel car has to operate under extremely variable conditions, ranging from low temperature during city driving to high temperature during motorway driving.

A paper by G. Smedler, G. Ahlstrom and

co-workers (Johnson Matthey) described how the extremely good low-temperature activities for carbon monoxide and hydrocarbons, neg- ligible sulphate storage and very good thermal stability, were combined in a catalyst, which also had good poison resistance and high lean nitrogen oxides performance, by controlling the interactions between the components in the platinum group metal based catalyst.

Several authors, including M. Iwasaki, N. Ikeya and co-workers (Ishikawajima-Harima Heavy Industries Co. Ltd.) described the good properties of platinum catalysts for nitrogen oxides removal under lean conditions, especially their stability, when water vapour and sulphur compounds are present, and lack of choking by carbon formation. However, they identify a need to improve the catalyst against nitrous oxide formation.

Two papers concerned with gasoline fuelled lean burn engines were presented. The first by N. Miyoshi, S. Matsumoto and colleagues (Toyota) and K. Kasahara (Cataler) described the mechanism of nitrogen oxides storage under lean operating conditions, the subsequent release and conversion, as the engine returned to stoichiometric control. This concept could enable the fuel economies of the lean burn engine to be combined with a good overall control of nitrogen oxides. This study used a Pt/Ba/A1203 catalyst, and it was postulated that an intermediate nitrate species is formed as the platinum catalyses nitric oxide oxidation to the dioxide.

The second paper, by A. Takami, T. Takemoto and colleagues of Mazda, described a new type of three-way catalyst containing platinum, rhodium and iridium as the active metals which, on a vehicle alternating between lean and stoichiometric conditions on the Japanese 1 0-mode cycle, achieved a significant reduction in nitrogen oxides. This area of gasoline-lean nitrogen oxides has received relatively little attention, and will be of interest for the future.

In summary, the 1995 SAE Congress continued to show the importance of catalyst solutions to combat automotive exhaust pollutants, and that platinum group metals will remain at the heart of that strategy. D.E.W.


Fundamentals and Applications of Metal-Hydrogen Systems INTERNATIONAL SYMPOSIUM ON RESEARCH INVOLVING PALLADIUM AND OTHER PLATINUM GROUP METALS

The fourth biennial International Symposium on Metal-Hydrogen Systems (Fundamentals and Applications) was held in the picturesque surroundings of Mount Fuji, in the Conference Centre, Fujiyoshida, near Tokyo, from the 6th to the 1 lth November 1994, under the joint Chairmanship of Professor Seijirau Suda of Kagakuin University and Professor Yuh Fukai of Chuo University. The direct involvement of the platinum group metals in this area of study was amply shown by the substantial amount of research that was reported, notably, by the amount of ongoing work on the phase and allied thermodynamic relationships of the palladium/hydrogen and palladium alloyihydrogen systems.

Also prominent were studies relating to the high mobility of the large concentrations of associated hydrogen interstitials which could be potentially available over a wide range of conditions and could be used for various applications, such as hydrogen purification membranes or film coatings to improve the electrode surfaces in metal-hydride batteries. The latter focus of interest formed the basis of conference keynote talks from D. Noreus of Stockholm University and Y. Lei of Zhejiang University.

Almost two hundred papers were submitted to the Symposium and presented in approximately equal numbers of oral and poster contributions. Over thirty of these presentations were concerned with studies of hydrogen interactions \?rith palladium or palladium alloyed with various elements - including other platinum group metals, particularly platinum and rhodium.

Hydride Formations and Structural Identification

The preparation of a new hydride, CaPd,H, at relatively high temperatures (650 K) and pressures (40 bar) from the direct interaction

of palladium and CaH,, was reported by D. Noreus of the University of Stockholm and K. Kadir of the National Research Institute, Osaka. Structurally the hydride is closely related to the recently reported superconducting hydride, NaPd,H,, which has a transition temperature of 1.6 K, and was the subject of an electronic structure analysis reported by A. Switendick of the National Engineering Laboratories, Idaho Falls, U.S.A.

In allied studies at higher upper temperature limits (- 900 K) and pressures (- 2500 bar) performed by G. Auferrmann and W. Bronger of the Institute of Inorganic Chemistry, Aachen, Germany, the formation of alkali ternary hydrides was reported from interactions between hydrides of A (where A represented sodium, potassium, rubidium or caesium) with metallic sponges of palladium and platinum, to give new compounds APtH, and APtH,, which were structurally analogous to APtC16 and NaPdH,, respectively.

The successful use of diamond anvil techniques to reduce the upper limits of temperature and pressure required for the formation of hydrides of various transition metals, including rhodium, were reported by M. Tkacz, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw.

Hydrogen Isotope Structural Studies Studies of neutron powder diffraction con-

cerned with the preferred interstitial positions in the Pd& structure which had been deuter- ated to a deuterium content corresponding to composition PdpSizDo.z6 were reported by Y. Anderson and colleagues of the Chemical Institute, University of Uppsala. Neutron difffaction measurements were also reported by E. Gray and colleagues, Universities of Brisbane, Sydney and Newcastle, and the Australian Nuclear Scientific and Technical Organisation,


Menai, Australia, on deuteron ordering in p- phase palladium-deuterium compositions at low temperatures, close to a 50 K anomaly region of the palladiuddeuterium system.

Certain palladium alloys seem to have shown particular attractions as materials for tritium storage. J. Holder and J. W. Wermer from the Westinghouse Technical Center, South Carolina, presented results of studies performed on alloys with rhodium, nickel, cobalt and chromium that were indicative of improvements concerning irreversible ageing reductions of their tritium storage capacities, and related increases of the slopes of p-n relationships over the phase transition regions, which seemed to signify the formation and retention of the ’He products from the decomposition of tritium.

Lattice Defect Influences Influences of increases in surface to substrate

ratios of palladium atoms within dispersed films and clusters continue to be reported as effect- ing modifications of phase relationships, and of physical and chemical characteristics.

These attempts to simulate the anticipated effects of estimated volume and surface area ratios of internal defects on the phase relationships of nanocrystalline clusters composed of 500 palladium atoms, were presented and compared with available experimental relationships by M. Leonard and R. Wolf of the Westinghouse Technical Center, South Carolina. The effects of controlled productions of dislocations at a H P-phase hydride transitions, and resultant formations of palladium-based materials with improved strength, special physical properties and also high plasticity, were reviewed by Professor V. A. Goltsov of the State Technical University, Donetsk, Ukraine.

Structural Rearrangements A keynote paper was presented by T. B.

Flanagan and H. Noh, both from the University of Vermont, which dealt with the influences of experimental pressurised hydrogen atmospheres and annealing conditions on the rearrangement of lattice structures in palladium alloys, including associated phase transitions.

“Superabundant vacancy” formation in palladium that resulted from annealing in hydrogen at - 800°C was reported by Professor Y. Fukai of Chuo University, Tokyo. Together with K. Watanabe, also of Chuo University, Y. Hayashi of Kyushu University, Fukuoka and Y. Sakamoto of the University of Nagasaki, Professor Fukai also reported on the separation of a PdsoRhzo alloy into palladium-richer and rhodium-richer regions after heating at - 550 to 600°C also in very high pressures of hydrogen. Essentially analogous findings of the separation of a PdsoPt,, alloy into preferentially palladium-rich and rhodium-rich regions after heating at temperatures between 448 and 573 K in atmospheres of hydrogen, were reported by Y. Sakamoto with H. Noh and T. B. Flanagan.

In contrast to these general findings of enhancement in compositional ordering after annealing in a hydrogen atmosphere, Sakamoto with K. Takao of the University of Nagasaki and T. B. Flanagan, reported experimental effects produced by the dissolved hydrogen acting usually to suppress ordering of palladium-rare earth solid solutions compositionally corresponding to Pd,Gd(Sm, Eu) alloy structures.

Defect and Phase Relationship Anelastic Effects

Internal friction (elastic energy dissipation) measurements associated with interaction effects related to hydrogen and dislocations in vibrating reeds made of nanocrystalline palladium, containing 2 and 4 atomic per cent hydrogen, were reported by H. Wipf and colleagues of the Universities of Darmstadt and Saarbrucken, and were compared with corresponding data for palladium in single crystal and coarse particle forms.

Measurements of internal friction over comparable temperature ranges (- 90 to 300 K) and vibration frequency, (- 3 kHz) were reported by F. M. Mazzolai and colleagues from the Universities of Perugia and Belfast, in studies with an extensive series of palladium-silver alloys covering wide ranges of hydrogen content. Results were correlated with corresponding


gradual changes in phase relationships and complementary structural interpretations of the palladium-silver-hydrogen system.

Diffusion Related Studies Studies of muon spin relaxation effects in

hydrogen-loaded Zr,Pd were reported by R. V. Havill and colleagues, University of Sheffield, measured over the temperature range 10 to 300 K. Results were discussed in terms of a muon tunnelling control mechanism changing to hydrogen diffusion control with increasing temperature. Studies of hydrogen permeation through palladium foils during modulations in imposed hydrogen pressure difference were discussed in a contribution from A. Altunogl and N. Braithwaite of the Open University Research Unit, Oxford. These techniques were represented as attractive methods for identifying control mechanisms between various alternative choices of surface and bulk processes.

Electrolytically Supplied Hydrogen Studies related to cold fusion possibilities

performed by M. Alquero and colleagues, University Autonoma Madrid, concerned electrolytic loading and hydrogen diffusion arising from measurements of pressures of deuterium and hydrogen gases evolved at palladium cathodes in closed cell systems. In similar studies made in conjunction with measurements of electrical resistivity, K. Kunimatsu and colleagues, Ih4RA Japan Co. Ltd., Sapporo, also reported pressure measurements in closed cells of hydrogen and deuterium gas evolved at palladium and palladium-rhodium alloy cathodes.

Palladium Coatings The advantages of using a combination of

palladium and nickel coated surfaces in a complex mischmetal-nickel based negative electrode, for producing improvements in hydrogen storage capacities and battery discharge rates of nickel-metal hydride batteries, were reported by M. Ganz of the C e n d Iron and Steel Research Institute, Beijing. A composite palladiudtitania film bielectrode, in conjunction with surface impedance measurements, was used in studies

of hydrogen permeation through titania films, reported by S. I. Pyun and colleagues of the Korea Institute of Science and Technology, Taejon. Measurements of the permeation of “ion-gun implanted” hydrogen through layers of palladium sputtered onto iron surfaces at 295 to 610 K, were reported by Y. Hayashi and colleagues of Kyushu University, Fukuoka, in work directed towards investigating conditions for hydrogen permeation through iron membranes.

Diffusion Coefficients and Strain Gradient Developments

Problems in electrolytically based methods for determining hydrogen diffusion coefficients, D,, in palladium were discussed in a review by R. V. Bucur and colleagues of the Universities of Uppsala, Nagasaki and Belfast, in which attention was drawn to influences on permeation rates of lattice strain gradients associated with “uphill effects”. Evidence of such “uphill effect” trans- fers, from lower to higher concentrations of lattice expanding hydrogen interstitials, had encouraged proposals advanced in a report by X. Q. Tong and colleagues, Universities of Birmingham, Nagasaki and Belfast, that analogous strain gradient and Gorsky Effect mechanisms might also provide a basis of explanation of hysteresis phenomena in p-c(n)- T relationships of the palladium-hydrogen and allied metal-hydrogen systems.

Observations of further “uphill effects” in the palladium-cerium-hydrogen system, recorded during electrochemical galvanostatic studies on palladium-cerium alloy membranes, were reported by Y. Sakamoto and colleagues, from Nagasaki, Belfast and Birmingham Universities.

Palladium Alloy-Hydrogen Systems The modifying effects of alloying elements

on the p-c(n)-T relationships and other characteristics of the palladium-hydrogen system, continue to be active areas of study.

Information about phase relationships, associated thermodynamic parameters and structural determinations for the hydrogen systems of the intermetallic compounds PdLi,,.,, and Pd2Li,,, were reported by Y. Sakamoto and


colleagues of the University of Nagasaki. Measurements were reported by A. Percheron- Guegan and colleagues (CNRS Meudon and CEA Bruyeres le Chatel) , of p-c(n) isotherms of deuterium pressure/deuterium content for series of palladium-platinum, palladium- rhodium and palladium(rhodium, platinum) alloys recorded over the temperature range 10 to 100°C. An increased cx t) P-phase deuteride transition pressure was noted with increasing alloying element content of up to - 10 per cent.

Electrical Resistivity Results from 7.5 to 20 K of electrical resistivity,

after hydrogen loading at 1 GPa pressure, of palladium, alloyed with nickel, ruthenium, rhodium, platinum and silver, were reported by A. Szafranski, Polish Academy of Sciences, Warsaw. Forms of the resistivity-temperature relationships were consistent with examples of Kondo Effect and spin-glass behaviour. Summaries and discussions of combined measurements of electrical resistivity-hydrogen content and p-c(n) relationships of hydrogen systems of palladium alloys with respective 4d and 5d elements paired in the same transition metal sub-group, were presented by R.-A. McNicholl and colleagues, Universities of Belfast, JafEna and Beijing.

Permeation Membranes Differences between the forms of p-c(n)

isotherms of palladium alloy-hydrogen systems have significance for the potential utilisation of

the alloys as hydrogen permeation membranes. A paper that was presented by Professor V. A. Goltsov dealt particularly with these aspects, presenting diagnostic diagrams which suggested the relative suitabilities of alternative alloying elements from the characterisation of their hydrogen solubilities and diffusion coefficients, under various combinations of hydrogen gas pressures, temperatures and problems caused by potential catalytic poisoning and corrosion.

Alloys of palladium with elements, such as silver, having larger atomic volume than palladium, have proved to be advantageous compositions when used for hydrogen permeation membranes.

A paper by Y. Sakamoto and colleagues from the University of Nagasaki, reported on extensive comparative studies of palladium-rich “expanded” ternary alloys of types palladium- yttrium(gado1inium)-silver and palladium- yttrium-indium(tin, lead), and complementary examinations of the influence of methane additions to input hydrogen permeation gas.

It is planned that the refereed papers presented at the symposium will be published in forth- coming volumes of the Journal of Alloys and Compounds.

The next symposium of the series will be held during 1996 in Switzerland at a venue still to be finalised and will be under the Chairmanship of Professor L. Schlapbach of the University of Fribourg. F.A.L.

Rhodium Express: ISSN 0869-7876 The Russian contribution to our know-

ledge of the platinum metals is incalculable; early research by gifted individuals led to the formation of the Institute for the Study of Platinum and Other Noble Metals at Petrograd, and in turn the first journal devoted exclusively to the platinum metals was founded to publish the research results of this Institute. Indeed, until its demise in 1955, this periodical was unique.

In 1993 a new Russian journal, entitled Rhodium Express, was launched to report

on the co-ordination chemistry of rhodium. Although the majority of the papers published to-date have reported Russian work, enabling readers to gain an early insight of topics currently being studied there, the number of contributions from other countries is increasing with time.

Further information about this useful addition to the literature can be obtained from The Editor: Yuri S. Varshavsky, P.O.B. 77, 198013 St. Petersburg, Russia; E-mail [email protected]; Fax: +7 (812) 251 4813.


Doctoral Theses from the C.I.S. In the belief that information on the academic platini$erous research carried out in countries of the former U.S.S. R . is not readily available in other parts of the world, a selection of abstracts of

doctoral theses will be published here from time to time; this includes the place and date of their defence.

Co-ordinative and Organometallic Compounds Based on the Stable l-Hydroxy-2,4,6,8- Tetrakis (tert-buty1)phenoxsazine-10-yl Radical I. V. KARSANOV, Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 16 October 1987, 127 pages, 20 Figs., 11 Tables, 153 Refs. Paramagnetic phenoxazinolate complexes of both man- sition and non-transition metals have been synthesised for the first time, and their structures and reac- tivities have been investigated. The presence of magnetic nuclei in the metal co-ordinative sphere has led to an increase in the stability of the complexes and added more informative features to their electron spin resonance spectra. The structures of mono-, di-, and tri-radical compounds of metals from Groups I-IV (K, Na, TI, Zn, Cd, Al, Ga, Sn, Pb), carbonyl ion radical complexes of platinum group metals (Pd, Pt, Ru, Rh, 0s) and their penta co-ordinative derivatives have been obtained.

The Magnetic Properties of Reduced PdFe Alloys at Super Low Temperatures, in the Ferromagnetic and Spin Glass States, by Mossbauer Spectroscopy A. w. PENTIN, Nuclear Physics Scientific Research Institute, Moscow State University, Moscow, 12 November 1987, 175 pages, 58 Figs., 5 Tables, 67 Refs. The percolating nature of ferromagnetism in PdFe alloy (containing 0.15 at.% of Pd) was established. The broad range of relaxation times in spin-glass alloy PdFe (containing 0.06 at.% Pd) has been investigated and the temperature dependence of the giant value magnetic moment established.

Isomerisation and Other Reactions of Diakylsulphoxide Complexes of Platinum(II) and Platinum(IV) A. I. MOISEEV, Leningrad Technological Institute, Leningrad, 24 November 1989,137 pages, 18 Figs., 21 Tables, 140 Refs. Methods for preparing Pt complexes with co-ordinated sulphoxides, nitriles and amides of carbonic acids have been elaborated. The effect of sulphoxides on the reactivity of other ligands in platinum complexes has been studied; and a correlation has been found between geomemcal isomerisation and the reaction conditions. The Pt(II) complexes promoted both strong hydrolysis of nitriles inside the inner sphere of the studied complexes and the deoxygenation of inner sphere sulphoxides. The possibility of using these complexes as catalysts and anti-cancer drugs is discussed.

The Synthesis and Properties of Dimeric Palladium(0) and Palladium(II) Complexes Containing Organophosphorus Ligands I. V. LOGINOVA, Kazan Chemical Technological Institute, Kazan, Tatarstan, 13 February 1990, 1 19 pages, 3 1 Figs., 2 1 Tables, 1 12 Refs. Methods to synthesise dimeric complexes of Pd(0) with organophosphorus ligands have been established, and the isomerisation of dimeric P d O complexes was found to proceed in non-aqueous solutions. Kinetic parameters were determined for the dissociation of such complexes, which was accompanied by Pd-Pd bond cleavage. A study of the catalytic activity of both Pd(0) and Pd(I) complexes for the hydrogenation of unsaturated compounds revealed high activity for palladium phosphinoxide complexes, but inhibited action for complexes containing a bridging carbonyl ligand. The effects on the reactivity from the composition and structure of the complexes resulted fkom the par- ticipation of the metal-metal bond, in, for example, dissociation and hydrogenation.

Adsorption and Electrocatalytic Properties of Dispersed Rhodium and Iridium z. A. ZIKRINA, Moscow State University, Moscow, 23 February 1990, 141 pages, 45 Figs., 3 Tables, 150 Refs. The aim of the study was to obtain highly dispersed rhodium and iridium doping on carbon supports and to investigate their electrocatalytical activity. Different forms of adsorbed CO molecules have been found on Ir/C electrodes, depending upon the sorption conditions. A method for preparing Ir/C electrodes, based on using reduced carbonic materials is proposed. The technique used for preparing a Rh/C electrode, which functions well as an electrocatalyst for maleic acid hydrogenation, is elaborated.

Formation of Hydrogenation Catalysts Based on Bisacetylacetonate and Bisacetate Palladium L. B. BELYKH, Irkutsk State University, Irkutsk, 10 October 1990, 216 pages, 49 Figs., 27 Tables, 164 Refs. Oxygen-containing palladium complexes and phosphorus (III) compounds (Pd(AcAc),, Pd(OAc),, PPh, and P(OEt),) have been studied as hydrogenation catalysts. Pd(AcAc)* and Pd(OAc)? have been reduced with hydrogen in aprotic solvents under mild conditions, promoted by water. The Pd blacks that formed were shown to be active in hydrogenation reactions. Redox interactions between Pd(AcAc)> and PPh,, Pd(OAc), and P(OEt), were found to take place in the presence of a stoichiometric amount of water. The main stages in catalyst preparation are established.

Plaiinum Metals Rev., 1995, 39, (2), 79 79

ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Microstructure and Mechanical Properties of Sputtered Platinum Films H. TOKURA, B. WINDOW, D. NEELY and M. SWAIN, Thin Solid Films, 1994, 253, (1-2), 344-348 The microstructure and mechanical properties of magnetron-sputtered Pt films deposited at low gas pressures of Ar and Xe on heated Si substrates were studied by XRD. The strain observed in Pt films is strongly dependent on deposition temperatures. Compressive stresses produced during deposition were greater for Ar-sputtered films, due to additional bombard- ment of the growing film by energetic Ar atoms from the cathode. Linewidths of the X-ray peaks are larger for Ar- than for Xe-sputtered films, since the films take in Ar. The strain in films deposited with Ar has a maximum at 100°C. There is a decrease in hardness with temperature for both films, but Ar-sputtered films are harder.

Adsorption of Nanometer-Sized Palladium Particles on Si(100) Surfaces E. P. BOONEKAMP, J. J. KELLY and L. G. J. FOKKINK, Langmuzr, 1994,10, (1 l ) , 40894094 Polymer-stabilised Pd particles adsorbed on Si initi- ated the growth of electroless Ni. The effect of the polymer (poly(vinylpyrro1idone)) on the surface coverage is described. Pd particles adsorbed strongly on Si, but almost no adsorption was observed on Si02. The-extreme substrate specificity of adsorption may be used for electroless deposition of metal patterns on semiconductor substrates. Electroless metal deposition from this electroless solution occurs only for r,,, < 1.5 x 10 '' atoms/cm', suggesting that a critical Pd particle density is needed for Ni deposition. By adjusting the polymer content of the sols the Pd concentration can be changed.

Changes in Crystallographic Orientation of Thin Foils of Palladium and Palladium Alloys after the Absorption of Hydrogen A. L. CABRERA, E. MORALES-LEAL, 1. HASEN and I K. SCHULLER, Catal. Lett., 1995, 30, ( 1 4 ) , 11-23 Studies of the adsorptionlabsorption of H, at room temperature by Pd, 16YoAg-Pd (1) and 5%Ru-Pd (2) foils showed that Hz readily diffused in the Pd and desorbed as one broad peak at - 650 K. HL also diffused in (1) and (2) foils but with a smaller diffusion constant. XRD studies of crystallographic orientation of the foils showed a preferential (l,l,O) orientation along the direction of rolling of the foils, which was destroyed after H, adsorption for Pd and (1) but unal- tered for (2). This orientation of the foils could be important in membrane fabrication, since H2 absorption by Pd is very dependent on surface orientation.

The Vibrational Excitations and the Position of Hydrogen in Nanocrystalline Palladium

H. GLEITER, Phys.: Condens. Matter., 1995, 7, (2),

The solubility and vibrational modes of H in nanocrystalline Pd were studied at 5 4.8 at.% H and the locations of the H were determined. At room temperature, no precipitation of the H in a hydride phase (P-phase) was observed. Solubility measurements show enhanced H solubility relative to coarse-grained Pd. This additional H was incorporated in the grain boundaries and at the surface of the grains.

In situ Comparison of Diffusivities for Hydrogen and Deuterium in Palladium c . J. LIHN, c. c . WAN and T P. PERNG, 3. Appl. Electrochem., 1995, 25, (l), 61-67 The diffusion behaviour of H and D in Pd was studied by an electrochemical permeation method using solutions of 0.1 M LiOD (in D?O) and 0.1 M LiOH (in H1O) and their mixtures as the catholytes. The results showed that the effective diffusivities increased with the concentration of D in the electrolyte. Comparison of corresponding permeation transients showed higher diffbsivity of D in Pd than H.

Surface Analysis of the PdCu(ll0) Single Crystal Alloy at Different Segregation Rates J . LOBODA-CACKOVIC. M. s . MOUSA and J. H. BLOCK, kcuum, 1995,46, (2), 89-96 The PdCu(l l0) plane, with Pd : Cu = 1 : 1 in the bulk, was prepared with various surface compositions, by applying cycles of Ar ion sputtering and annealing at 420 c T,,, < 820 K. A smooth Pd-rich surface was produced by high temperature treatment of the surface followed by low temperature sputtering and annealing at T,\n below that of Cu segregation, - 550 K. A large number of sputtering and annealing cycles without prior high TSN gave a rough surface, which allowed Cu atoms lying beneath the surface to react.

Transmission Electron Microscopy and X-ray Diffraction Investigation of Phase Formation and Transition between Pd,Si and PdSi in Pd Thin Films on (111)Si J. F. CHEN and L. J. cHEN, Mater. Chem. Phys., 1995,

Studies of the phase formation and transition between PdS i and PdSi in Pd thin films on (1 11)Si showed that in as-deposited and 200Cl l h annealed Pd(30 nm)/( 11 1)Si samples, epitaxial PdSi coexisted with the unreacted Pd layer. At annealing temperatures 250-800,850 and 900-1O0O0C, only epitaxial Pd,Si, PdSi and Pd2Si phases, and mainly PdzSi and PdSi, were found, respectively. PdSi and PdSi were the stable phases at 300-800 and 850-875"C, respectively.

U. STUHR, H. WIPF, T. J. UDOVIC, I. WEISSMULLER and

219-230

39, (2), 229-235


Heat of Crystallization and Microstructure of Amorphous Pd,Si,, and F e d , Alloys E. ASAYAMA, H. IMAMURA, H. TAKEBE and K. MOIUNAGA, Mater. Trans.,3ZM, 1994, 35, (lo), 708-715 The correlation between the heat of crystallisation (1) and microstructure of PdazSi,, and FeaoBZo alloys was studied on alloys prepared by a melt-spinning method with various rotating velocities of the Cu wheel. X- ray amorphous Pd,,Si,, alloy, whose XRD pattern showed a halo, had a uniform microstructure without crystals, that is glass. The critical cooling rate for the formation of the X-ray amorphous phase in Pdn2Si,, alloys is the minimum cooling rate to avoid detectable crystal formation. (1) is proposed as a para- meter of the degree of non-crystallinity for the alloys.

Bulk Nanophase Pd,Si,, Directly Synthesized by High Pressure Quenching from Melt of Alloy z.-c . QIN, Y. LIU, Y. ZHANG, w. LIU and w.-K. WANG, 3: Muter. Sci. Len., 1995, 14, (3), 209-210 Bulk nanophase Pd,,Si,, was prepared directly by quenching the melt of the alloy to room temperature under high pressure. The matrix alloy was prepared by arc-melting a mixture of pure Pd and Si in an Ar atmosphere. Bulk nanophase metal or alloy was thus obtained without preparing ultrahe particles or atom clusters. Also, the original alloy need not trans- form into the amorphous state. There are no voids or small pores in the bulk nanophase materials prepared by this route, due to their direct synthesis from the melt. Pressure used during quenching is a most important factor in synthesising these materials.

Mechanism of Low-Temperature Rhodium Oxidation A. N. SAIANOV and v. I. SAVCHENKO, Kinet. Katal., 1994, 35, (5), 780-785 Interactions of 0, with Rh(100) and polycrystalline Rh were studied at O2 pressures of 10 5-103 Pa and 400-600 K. At O2 pressure 2 10 Pa, a F&O, layer was formed and its volume increased according to a mechanism of low-temperature oxidation of metals by Cabrera-Mott. The increase in the layer thickness depends on both the 0, pressure and the temperature. The data show a weak structural effect from the Rh surface on the oxidation process.

Rhodium Segregation in Dilute Silver- Rhodium Alloys K. KROLAS and M. STEFWIK, Acra Metall. Mater., 1995, 43, (l), 51-57 Segregation of Rh in Ag-Rh alloys has been studied by perturbed angular correlation of '(-rays emitted in the nuclear decay of radioactive "'In. The formation of impurity complexes, of an "'In probe atom and one or more Rh atoms, was observed as a function of annealing time and temperature. Rh atoms starts to aggregate at - 600 K. The solute Rh atom concentration (1) depended on the nominal alloy concentration (2) and temperature. (1) increased as a function of (2) up to about 0.04 at.% and was then unchanged for 0.1-0.5 at.% Rh. (1) was 3 times larger at the melting point, 1234 K, than at 750 K.

Kondo Coherence Gap and Superconductivity in the Ce, -I La.RhSb System S. K. MALIK, L. MENON, K. GHOSH and S. WSHNAN, Phys. Rev. B, 1995,51, (l), 399-403 The gap formation in the electronic density of states in CeRhSb, a mixed valent Ce-based compound which undergoes a rapid rise in resistivity at low temperatures attributable to the gap opening, has been investigated by addition of La. The gap formation was rapidly suppressed on replacing a small amount of Ce by non-magnetic La, but susceptibility continued to show mixed-valent behaviour. With increased La concentration, the susceptibility of the compounds in the solid solution Ce, .La,RhSb gradually changes from mixed-valent type to Curie-Weiss type.

Magnetic Properties of New M-Type Hexaferrites BaFe,Z- 2xIrxCoxO19 B. sum and H. VINCENT,~: Magn. M a p . Maw.., 1995, 139,364-370 M-type BaFe,,O,, hexagonal ferrite powders with partial substitution x Ir" + x Co" for 2x Fe" were produced by sintering. The intrinsic uniaxial anisotropy becomes planar in the title compound for x = 0.5. The saturation magnetisation decreased linearly from 7 1.2 to 58.9 emdg with increasing doping content of 0 to 0.8. The coercivity dropped sharply for x = 0.3 and the ordering temperature decreased linearly with increasing x. The substitution of x = 0.6 resulted in a material with planar anisotropy.

CHEMICAL COMPOUNDS Synthesis and Properties of Platinum Complexes of Fullerenes (C, and Go)

KIKUCHI, I. IKEMOTO and Y. ACHIBA, Fullerene Sci. Technol., 1995, 3, (l), 1-9 Pt complexes of fullerenes were prepared by the reaction of C,, and C,, with (CH,=CH,)Pt(PPh,), or Pt(PEt,),. The crude Pt complexes were dissolved in benzene-hexane (1) and purified by column chro- matography on Si02 gel. Elution using (1) (1:2) gave the pure (Et,P),Pt(q'-C,,J complex in 68% yield with 32% of recovered C6,). The X-ray data of the C,,,-Pt complex showed definite bond lengths and angles.

The Extraordinary Properties of Electro- chemically Synthesized Cluster Compound Ki.J't( GO,), L. xu and s. DONG, Electrochim. Acta, 1994, 39, (17),

The conducting Pt cluster compound K, ,,Pt(C,O,), (1) was synthesised on a glassy C electrode by elec- trooxidation of K,Pt(C,O,), by a single potential step and cyclic voltammetry. (1) is fibrous with excellent conductivity and is effective for the electroactive species in solution, since its plateau current has the same potential as the peak current. (1) can be used in organic films of chemically modified electrodes as a conductor. An ultramicro electrode could be made from a single crystal of ( I ) , as it has linear crystal morphology and anisotropic conductivity.

M. IYODA, Y. OGAWA, H. MATSUYAMA, H. UENO, K.

2599-2604


Organometallic Hydrides as Reactants in Fullerene Chemistry. The Interaction of C,, and C, Fullerenes with HIr(CO)(PPh,), A. v. USATOV, E. v. VORONTSOV, L. E. VINOGRADOVA and w. N. NOVIKOV, Izv. Akad. Nauk, Ser. Khim., 1994,

Ir hydride HIr(CO)(PPhJ3 reacted with fullerenes C,, and C,,, yielding (11'-C,,)IrH(CO)(PPh,), ( n = 60, 70) complexes. Their composition, configuration and position of a double bond in a fullerene moiety co-ordinated with Ir atom were studied by IR, to compare the deuterio forms, and by 'H and "P spectroscopies.

Preparations of Ultrafine Ir0,-SnO, Binary Oxide Particles by a Sol-Gel Process Y. MURAKAMI, H. OHKAWAUCHI, M. ITO, K. YAHIKOZAWA and Y TAKASU, Electrochim. Acra, 1994, 39, (17), 2551-2554 Ultrafine particles of Ir (1 00%) and Sn (100%) oxides of homogeneous composition, and four Ir0,-SnO, binary oxides with different 1r:Sn atomic ratios, were prepared by a sol-gel process. The unit length of rutile- type (Ir, Sn)O, cell decreased with increasing Ir'+ content. The Ir-Sn binary oxides crystallised to the (Ir, Sn)O, rutile-type phase at a lower temperature than Ir oxide to Ir02.

Osmium Carbonyl Cluster Growth on Self- Assembled (3-Mercaptopropyl)trimethoxy- silane on a Gold Surface A. MORNEAU, A. MANIVANNAN and c. R. CABRERA, Langmuir, 1994, 10, (1 l), 3940-3942 The growth of an 0 s carbonyl cluster on a self-assembled alkylsiloxanethiol monolayer, (3-mercapto- propy1)mmethoxysilane (1) on a Au( 1 1 1) surface was studied by observing the surface reaction of Osl(CO),,(NCCH,) with (1). The 0 s clusterreacted with (1) destroying the well-ordered thiol surface forming several cluster aggregates of 10-22% diameter.

Triosmium Cluster Derivatives of [60] Fullerene J. T. PARK, J.-J. CHO and H. SONG, J. Chem. Soc., Chenz. Commun., 1995, (l), 15-16 Triosmium carbonyl cluster derivatives of [60]- fullerene, Os, (CO) I I (q2-C6"), Os,(CO), ,,(NCMe) ($-

C,,,) were prepared. A definite structural assignment was made using spectroscopic data.

A Zwitterionic Cluster Compound: Synthesis and Characterisation of the Triphenyl- phosphoniocyclopentadienide Derivative [R&( CO)i,(IIS-CBJ'Ph,)] A. J. BLAKE, B. F. G. JOHNSON, s. PARSONS and D. s. SHEPHARD, 3 Chem. soc., Dalton Trans., 1995, (3), 495-496 The octahedral cluster [Ru6C(CO),,(qi-C5H,PPh,)] was prepared by the reaction of [Ru,C(CO),,] with trimethylamine N-oxide in the presence of C,H,PPh,. Crystal and molecular structure studies showed that this Ru organocluster complex contains an apically co-ordinated cyclopentadienyl unit.

(9), 1661-1665

Cm), Os,(CO) io(PPhi)(q'-Cw) and OS,(CO)dF'PhJ~

Photophysical Properties of Monomeric and Oligomeric Ruthenium(I1) Porphyrins M. IKONEN, D. GUEZ, v . MARVAUD and D. MARKOVITSI, Chem. Phys. Lett., 1994, 231, (l), 93-97 The photophysical properties of three Ru(I1) porphyrins: RuTBP(CO)(EtOH) (l), R U T B P ( ~ ~ Z ) ~ (2) and [RuTBP@yz)],, (3) where TBP = tetrakis(3,5-di- rerr-butyl-4-hydroxyphenyl) porphyrin and pyz = pyrazine, are discussed. The lowest excited state of (2) is the triplet metal-to-ring charge transfer having weak luminescence with quantum yield of 0.6 x 10 ' and a lifetime of 5 1 ns. (3) behaves as "insu- lated wire" which is confirmed by the small Stokes shift associated with the C T emission.

ELECTROCHEMISTRY Electropolymerization of 2-Hydroxy-3- Aminophenazine (HAPh): Properties of pHAF'h Films and Kinetics of Oxidation and Incorporation of Dihydroxybenzenes at Pt/pHAPh Electrodes G. KOKKINIDIS, A. PAPOUTSIS and I. POULIOS, J. Electroanal. Chem., 1994, 319, (1-2), 379-387 A stable redox active polymer (pHAPh) with structure and redox properties close to those of poly(o- phenylenediamine) and poly(o-aminophenol) was prepared after oxidative electropolymerisation of 2- hydroxy-3-aminophenazine (HAPh) on Pt, Au, glassy C and I T 0 electrodes. Rotating PdpHAFh disc electrode studies showed that dihydroxybenzenes were incorporated into the pHAPh film in the reduced state, but p-benzoquinone was added in its oxidised state.

Electro-Oxidation Mechanisms of Methanol and Formic Acid on Pt-Ru Alloy Surfaces N. M. MARKOVIC, H. A. GASTEIGER, P. N. ROSS, X. JIANG, I. VILLEGAS and M. J. WEAVER, Electrochim. Acta, 1995, 40, (l), 91-98 The extent of adsorbed CO produced at Pt, Ru and Pt-Ru alloy electrodes during MeOH and formic acid oxidation in acidic supporting electrolyte was studied by voltammetry and spectroscopy. The addition of- 10 at.% Ru to Pt decreased the quasi-steady-state level of adsorbed CO, at any potential, in either solution. This was even more pronounced for 50% Ru alloy, when the CO coverage was reduced to < 10%.

Palladium Metal Microparticles Incorporation in Poly (N-Substituted Pyrrole) Film-Coated Electrode N. TAKANO, M. NAKABAYASHI and N. TAKENO, Denki Kagaku, 1994,62, (12), 1238-1239 I'd metal was incorporated into new poly (N-linear alkyl substituted pyrrole) film-coated electrodes by immersing the electrodes into Na,PdCl, solution. The substituents were CjH, , (a), C5HI ,0H (b) and CjH,,,OMe (c). Currendvoltage curves for H2 evolution in the buffer showed that (a)/Pd and (c)/Pd electrodes had smaller changes in the cathodic current than did the (b)/Pd electrode, which had high H evolution currents at lower potentials and high stability.


Electrochemical Formation of Pd-Li Alloys in LiCI-KCl Eutectic Melts T. NOHIRA, K. AMFZAWA and Y. rroJ Appl. Ehcmhem.,

Cyclic voltammetry, open-circuit potentiomeuy and XRD were used to examine the electrochemical formation of Pd-Li alloys and Pd-rare earth alloys via deposition of Li onto a Pd electrode in molten LiCl- KC1 eutectic melts. Various Pd-Li alloy phases were formed, such as LiPd,, LiPd2, LiPd and Li,Pd, at 1.05, 0.64,0.53 and 0.20 V vs. Li’fi at 450”C, respectively. The results provide data on the electrochemical window of the molten LiC1-KCl system for Pd-rare earth alloy electrochemical formation using Pd electrodes.

Cathodic Reduction of Nicotinamide Coenzyme (NAD’) Mediated with Rhodium Complex Immobilized on Electrode Surface Y. SHIMIZU, A. KITANI, s. ITO and K. SASAKI, Denki Kagaku, 1994,62, (12), 1233-1234 The reduction ofNAD’, mediated with [Rh(bpy),]” complex immobilised on an electrode surface, was performed to obtain the highly selective regeneration of NADH. (1) was immobilised by ion-exchange onto the hydrogel coated electrode. The cathodic reduction of NAD’ was performed in a divided electrolysis cell in a b d e r (PH = 8.0) containing 1 mh4 NAD’, using a Pt plate and a saturated calomel electrode as the counter and the reference electrodes, respectively. [Rh(bpy),]”hydrogel electrode used for repeated runs of NAD’ reduction showed excellent stability.

1995,25, (l), 48-53

PHOTOCONVERSION Photoreduction of Water by the System of C- Platinum-Methylviologen

Y. OKADA and J. NISHIMURA, Fullerene Sci. Technol., 1995, 3, (l), 3 7 4 3 A fullerene-Pt-methylviologen photocatalytic system was used successfully to reduce H,O under photo- irradiation through a Pyrex filter. The light is absorbed by the photocatalyst, and the valence electron is lifted to the conduction band level and transferred to the methylviologen and then to colloidal Pt. At the Pt surface, H,O is reduced by the electron. The maximum evolution of H2 was 1 10 p o l h e a d space of 5 mV5 h.

Surface States in the Band-Gap for Pt- Deposited p-InF’ Photoelectrochemical Cells H. KOBAYASHI, F. MIZUNO and Y. NAKATO, Appl. SUI$ Sci., 1994,81, (4), 399-408 The effect of surface states in the band-gap for Pt- deposited p-InP( 100) photoelectrochemical cells on the cell performance was studied. The maximum of the surface state density was located at - 0.16 eV above the InP valence-band maximum and these states are in a negative or neutral charge state, depending on the electrode potential. An increase in the barrier height is nearly proportional to the decrease in the surface state density. The decrease of the photovolt- age caused by lowering the barrier height in the pInP is due to the static negative charge in the surface states.

M. IGARASHI, M. FUKUDA, M.TAKI,T. TAG0.T. MINOWA,

Photogeneration of Hydrogen Using Visible Light with UndopedlDoped a-Fe,O, in the Presence of Methyl Viologen K. GURUNATHAN and P. MARUTHAMUTHU, Int. 3. Hydrogen Energy, 1995, 20, (4), 287-295 Visible light-induced H, production from H,O split- ting reactions was studied by using undoped or Rh(III)/Cu(II)-doped, with or without RuO, loaded a-Fe,O, at various pH, with methyl viologen as an electron relay. Loading with Rh(II1) and Cu(I1) ions increased the HI production efficiency of the photocatalyst, with R h o being more effective than C u m in increasing the photocatalytic activity of a-Fe,O,. The increased activity is explained via the role of the metal ions loaded in the photogenerated electron- hole separation. Simultaneous loading of RuO, and Rh(III)/Cu(II) ions further increased the efficiency.

Photocatalytic Reduction of Nitrogen over (Fe, Ru or Os)/TiO, Catalysts N. N. RAO, s. DUBE and M. P. NATARAJAN, Appl. Catal. B: Environ., 1994, 5 , (1-2), 33-42 Irradiated aqueous suspensions of Ru, 0 s or Fe/TiO, catalysts were active for the photocatalytic reduction of N, to NH?. The catalytic activity was in order Ru > Fe > Os, but the reverse order was found for the stability of the catalysts with respect to NH, formation. However, the catalysts appear to lose activity due to the disappearance of Ti” sites.

Ru(bpy)F Bound to an Insoluble Polymeric Phase. Reductive Luminescence Quenching J. L. BOURDELANDE, J. FONT, G. MARQUES and D. SALVATIERRA,J. Phowchem. Phowbiol. A: Chem., 1995,

The reductive quenching of excited Ru(bpy)l” (bpy = bipyridyl) covalently bound to insoluble polystyrene showed two different polymeric environments and two diEerent photochemical behaviours for the excited complex. It is concluded that only those Ru(bpy)? units linked to the surface of the bead (functional groups, up to 1.5%) can be deactivated by N,N- dimethylaniline by rapid reductive quenching after irradiation while the rest remain unavailable in the interior of the bead.

85, (1-2), 143-145

ELECTRODEPOSITION AND SURFACE COATINGS Thermal Cycling of Iridium Coatings on Isotropic Graphite K. MUMTAZ, J. ECHIGOYA, H. ENOKI, T. HIRAI and Y. SHIN DO,^ Mater. Sci., 1995, 30, (2), 465-472 Thermal cycling and long-term heat testing on Ir- coated isotropic graphite substrates showed variation in the surface morphology at 30C2173 K. The colum- nar structure was retained after thermal cycling at 30C1873 K, but this was replaced by dense equiaxed grains whose size increased with time and temperature at high-temperature thermal cycling or heating at 1873 K for 90 ks. The pores in the coating which appeared after thermal cycling at 30C1873 K dimin- ished after high-temperature thermal cycling.


APPARATUS AND TECHNIQUE Dry Etching of Palladium Thin Films in Fluorine Containing Plasmas: X-ray Photoelectron Spectroscopy Investigation F. FRACASSI, R. DAGOSTINO and A. CACUCCI, J. Vu. Sci. Technol., 1995, 13, (l), 63-66 The dry etching process of Pd thin films was studied in Ar-CF, and Ar-CF,-02 glow discharges by per- forming etch rate measurements and XPS analyses. The etching process was physical sputtering; F atoms react with Pd forming a fluorinated layer, such as PdF, which has a lower sputtering rate than metallic Pd. By increasing the amount of Or in the feed gas the surface CF, contamination is reduced, gas phase F atom concentration increases, but the etching rate remains - 8 times lower than that with 100% Ar.

Electrochemical and Mirage Detection Studies of Sputtered Iridium Oxide Films M. BARDIN, P. LOHEAC, M. PETIT, v. PLICHON and N. RICHARD, N e w 3 Chem., 1995,19, (l) , 59-63 Electrochemical measurements and ion flux detection on sputtered Ir oxide films (SIROFS) in contact with aqueous solutions of variable pH or neutral alkali electrolytes were carried out. The shape of the voltammograms was highly dependent on the electrolyte, changing from a capacitive response to a double-peak shape. The probe beam deflection technique (mirage effect) showed that capacitive voltammograms correspond to an H or HO exchange, while peak-shaped voltammograms display a complex double ion flux. The charge of the Ir oxide films is mainly faradaic, regardless of the voltammogram shape.

Os(phen),(dppz)”: A Red-Emitting DNA Probe R. E. HOLMLIN and J. K. BARTON, Inorg. Chem. 1995,

An 0 s bi(1,lO-phenanthroiine) dipyrido[3,2-a-:Z,Y- clphenazine complex, Os@hen),dppz,+, was prepared and tested as a DNA probe. When DNA was present in solution with the 0 s complex, it emitted red light of h 700-800 nm with lifetimes 10 ns, and could be used as a fast diagnostic DNA probe.

34, (l), 7-8

HETEROGENEOUS CATALYSIS Catalytic Oxidation of Dichloromethane, Chloroform, and Their Binary Mixtures over a Platinum Alumina Catalyst D. M. PAPENMEIER and J. A. ROSSIN, Ind. Eng. Chem. Res., 1994, 33, (12), 3094-3103 The complete catalytic oxidation of CH,Cl, (l), CHCl, (2) and their mixtures in humid air was studied over a 3% W K - ~ AIzO, catalyst in a fixed bed catalytic reactor at 300-400°C. The oxidation of (1) and (2) as pure compounds was non-linear in the concentration of (1) and zeroth order in the concentration of 0,. This was explained by the formation of HC1 during the oxidation which decreased the reaction rate. The h a 1 reaction rate expressions can predict catalyst performance during the oxidation of (1):(2) mixtures.

The In5uence of Sulfur Dioxide on Propane Oxidation Activity over Supported Platinum and Palladium c. P. HUBBARD, K. orro, H. s. GANDHI and K. Y. s. NG, Catal. Lett., 1995, 30, (1-4), 41-51 Four catalysts, Pt/y-Al,O,, Pt/ZrO,, Pd/y-Al,O, and PdZrO,, were studied in order to compare the known effects of metal-support activity and sulphate on Pt, with Pd, for propane oxidation. Metal loading was 50.05 wt.%. In contrast to Pt, sulphation did not promote propane oxidation on Pdy-ALO, and PdZrO, was less active than Pdly-Al,03. The acid strength of ZrO, was significantly increased after sulphation, whde that of y-Al,O, was only slightly raised.

Investigation of Pt/AI,O, and Pd/AI,O, Catalysts for the Combustion of Methane at Low Concentrations R. BURCH and P. K. LOADER, Awl. Catal. B: Environ., 1994, 5 , (1-2), 149-164 Pt/Al,O, and Pd/Al,O, catalysts, prepared from CI- free precursors, were studied during the combustion of CH, under lean, stoichiometric and rich conditions using dilute mixtures. Under lean conditions, and at low conversions under stoichiometric or rich conditions, PdAl,O, was the more effective catalyst, but at higher conversions Pt/A1,0, was more active. This change over is associated with a “light-off’ effect observed with Pt/Al,O,. Pt can be a more effective catalyst than I’d for CH, combustion under real conditions for natural gas fuelled vehicles.

Metal-Support Interaction in Pt/C Catalysts. Influence of the Support Surface Chemistry and the Metal Precursor M. C. ROMAN-MARTiNEZ, D. CAZORLA-AMOROS, A. LINARES-SOLANO, C. SALINAS-MARTINEZ DE LECEA, H. YAMASHITA a n d ~ . m p O , Carbon, 1995,33, (l), 3-13 The effect of support surface chemistry and metal precursor species on Pt/C properties was studied using the char of a phenolformaldehyde polymer as the C source and H,PtCl, acid and [Pt(NHJr]C1, as precursors. The Pt precursor distribution on the supports, and the metal precursor-support interaction, depended on the support surface. The surface oxidation of the supports has a negative effect on the Pt dispersion. The lower the number of surface 0 complexes, the higher the metal dispersion.

Catalytic Behaviour of Carbon-Supported FeM (M = Ru, Pt) in Pyridine Hydrodenitrogenation A. GUERRERO-RUIZ, A. SEPULVEDA-ESCRIBANO, I. RODRIGUEZ-RAMOS, A. LOPEZ-AGUDO and J. L. G. FIERRO, Fuel, 1995, 74, (2), 279-283 C-supported one-component Fe, Ru and Pt, and two- component FeRu and FePt catalysts were used for hydrodenitrogenation ofpyridine at 3.0 MPa and 573 K. Fe and Ru monocomponent catalysts were sulphided, but Pt partly preserved its metallic character. A decrease in the Fe:C ratio and a big increase in the Pt:C ratio in the two-component catalysts showed that Fe is redispersed during incorporation of Pt, and Pt is deposited mainly at the outer surface.


Performance and Durability of Pt-MFI Zeolite Catalyst for Selective Reduction of Nitrogen Monoxide in Actual Diesel Engine Exhaust

J. GUO, M. KONNO, T. CHIKAHISA and T. MURAYAMA, Appl. Catal. B: Environ., 1994, 5 , (1-2), Ll-L5 Selective catalytic reduction of NO by hydrocarbon in an oxidising atmosphere was studied over Pt-MFI zeolite (Pt-MFI) in synthesised or actual diesel engine exhaust gases. The activity of Pt-MFI in the synthesised gas, containing 10% H,O, changed in the early stage of use, but levelled off after 15&200 h, and then

M. IWAMOTO, H. YAHIRO, H. KHIL SHIN, M. WATANABE,

Synthesis of Hydroxamic Acids: Pd/BaSO, as a New Catalyst for the Deprotection of 0- Benzyl Hydroxamates

DOHERTY, Tecrahedron h t . , 1995, 36, (2), 197-200 5% PdBaSO, was found to be an efficient catalyst in the deprotection of 0-benzyl hydroxamates, dissolved in MeOH, by hydrogenation to give the corresponding hydroxamic acids without further reduction to amides. The reaction mixture was filtered and the filtrate evaporated to give the desired product in good to excellent yields after purification. Various

S . S. NIKAM, B. E. KORNBERG, D. R. JOHNSON and A. M.

was constant for > 800 h. The Pt-MH catalyst had stable activity at 423-773 K and 10,000-150,000ih (gas hourly space velocity) in actual engine exhaust with light oil as a fuel. The amount of NO reduction increased linearly upon addition of ethylene.

hydroxamic acids were synthesised.

Hydro&n the Bicarbonamormate Reaction. Studies on the Activity of Pd Catalysts

Synthesis of Highly Active Superacids of S041Zr02 with Ir, Pt, Rh, Ru, Os, and Pd Substances for Reaction of Butane M. HINO and K. ARATA, cazal. h t . , 1995, 30, (I+),

Highly acidic catalysts, which are more acidic than the S04/Zr0, superacid and have an acid strength H, 2 -16.04, were prepared by kneading Zr(OH), with NH, sulphate together with chlorides of Ir, Pt, Rh, Ru, 0 s and Pd, followed by calcining in air at 600°C. The metal concentration was equivalent to that of Pt, of 7.5 wt.%, based on the hydroxide. The catalysts with Ir and Pt materials had the highest activity for the skeletal isomerisation of butane to isobutane.

Preparation of Bimetallic Pt-Au Catalysts by Redox Reaction: Characterisation by XRD and SAXS V. BERTIN, P. BOSCH, G. DEL ANGEL, R G O M E Z , J. BARBIER and P. MAR~COT, 'j? Chim. Phys., Phys.-Chim. Biol., 1995, 92, (l), 120-133 Bimetallic Pt-Au/SiO, catalysts were prepared by surface redox reactions by introducing Au as AuCI; reduced on the Pt surface either by H, preadsorbed or by direct oxidation of Pto by AuC1;. Spectroscopic studies showed that the bimetallic aggregates are formed from Au particles deposited on Pt particles, with reciprocal diffusion between the two metals.

Catalytic Synthesis of Unsaturated Nitriles from NO-Alkane or NO-Alkene on Pt-SdSiO,

Chem. Commun., 1995, (3), 329-330 Unsaturated nitriles were produced on Pt-Sn/SiO, catalysts, prepared by the selective bimetallic CVD reaction of SnMe, with Pt particles on SiO,. The yields of acrylonitrile obtained from NO + propene and methacrylonitrile from NO + isobutene and NO + isobutane, had selectivities of- 70-93%, when compared with little activity and selectivity with unmodified Pt/SiO,. Both the rate and selectivity of acrylonitrile formation increased with Sn content and reached a maxima at Sn:Pt = 0.2. NO dissociation and ally1 hydrogen abstraction are thus promoted on Pt-Sn bimetallic ensemble sites.

25-30

T. INOUE, K. TOMISHIGE and Y. IWASAWA, 'j? C h m . SOC.,

H. KRAMER, M. LEVY and A. WARSHAWSKY, Int. J. Hydrogen Energy, 1995,20, (3), 229-233 Studies of storage and generation of H, within the bicarbonatelformate reaction, showed that the Pd catalyst used loses its activity with time, but can be regenerated by air oxidation. CO poisoned the catalyst in both the forward and the back reactions. The Pd catalysts, based on polymer stabilised microdispersions, prepared from Na2PdC14 and NaH,PO,, were active as the C-supported catalysts for H, generation. H, could be generated at pressures as high as 20 atm.

The Effect of Alumina Phase Structure on the Dispersion of RhodidAlumina Catalysts R. w. MCCABE, R. K. USMEN, K. OBER and H. s. G m m , 'j? Cacal., 1995, 151, (2), 385-393 Rh was impregnated onto 6,8 and a ALO, at a loading of 0.6 p o l Rh/mz and the resultant Rh/Al,O, catalysts were hydrothermally aged by treating in 10% HzO/air at 1223 K for 24 h. TPR and other measurements identified 3 broad Rh forms: occluded, strongly interacted and non-interacted. A pronounced loading effect was observed for the a-AlzO,. The combined effects of an a-Al,O, support, steam/air high temperature ageing prior to Rh deposition at < 1 poVmz, maximised Rh dispersion and produced a more active catalyst than Rh deposited on higher surface area transitional AlzO,.

Rh-Loaded CeO2-ZrO2 Solid Solutions as Highly Efficient Oxygen Exchangers: Dependence of the Reduction Behavior and the Oxygen Storage Capacity on the Structural Properties

S. MERlANI, A. TROVARELLI and M. GRAZIANI, 'j? cacal.,

Monoclinic, tetragonal and cubic structures of the binary Rh-loaded CeOz-ZrOz systems were reported during TPR in a HJAr mixture with 10-90% ZrO,. Incorporation of ZrO, into a solid solution with CeO, strongly promotes bulk reduction of the Rh-loaded solid solutions compared with Rh/CeO,. This structural dependence is attributed to a higher 0 mobility in the cubic structure compared to the tetragonal and monoclinic ones.

P. FORNASIERO, R DI MONTE, G. RANGA RAO, J. KASPAR,

1995, 151, (l), 168-177

Platinum Mecals Rev., 1995, 39, ( 2 ) 85

HOMOGENEOUS CATALYSIS Palladium- and Platinum-Catalyzed Coupling Reactions of Allyloxy Aromatics with Hydridosilanes and Hydridosiloxanes: Novel Liquid CrystallinelOrganosilane Materials A. SELLINGER, R. M. LAINE, V. C H U and C. VINEY, 3. Polymer Sci. A, Polymer Chem., 1994, 32 , (16), 3069-3089 Pt- a’nd Pd-catalysed reactions of allyloxyaromatic mono- and diesters with selected silanes were studied to develop simple methods of forming liquid crystal (LC)/siloxane and LC/silsesquioxane polymers. Pt complexes catalysed hydrosilylation to give primarily (< 80% selectivity at 100% conversion) terminal sily- lation of the allyloxys, with Pt-l,3-divinyltetramethyl- disiloxane giving the cleanest reactions under the mildest conditions. Ph,P[Pd(dba)2/Ph,P] gave the cleanest oxysilylation reactions.

Palladium Catalysed AIlylic Substitution Reactions of Prochiral and Racemic Ally1 Acetates G. J. DAWSON, J. M. J. WILLIAMS and s. J. COOTE, Terrahedron. Len., 1995, 36, (3), 461462 The reaction of non-symmetrical ally1 acetates and sodiodimethylmalonate catalysed by [Pd (allyl)Cl] gave high yields and enantioselectivities of 5 9 9 % ee, using a diphenylphosphinoaryl oxazoline ligand (1). It is assumed that alternative x-ally1 Pd complexes can interconvert by the n-o-x mechanism. Thus substrates where the termini of Pd ally1 intermediate are non-equivalent give enantioselective reactions with (1).

The Kinetics and Mechanism of Styrene Hydrocarboxylation Catalysed by PdCl,(Ph$), Complex. 11. The Effect of the Styrene, Palladium Complex and Triphenylphosphine Concentration on the Rate and Regioselectivity of the Process W. G. NOSKOV and E. s. PETROV, Kinet. Katal., 1994,

The effect of a catalytic system containing styrene PdCl,(Ph,P), and Ph,P, on the initial rate of formation of hydrocarboxylation products 3- and 2-phenyl- propionic acid, (1) and (2), respectively, was studied. The rates of formation of both compounds were linear depending on the concentrations. The formation of (2) increased with styrene concentration, but with increasing PhP, concentration the formation of (2) greatly decreased; H,O enhanced the decrease.

Synthesis of Allylsilanes by Palladium(0) Catalyzed Reduction of Trialkylsiiylallyl Esters J. OLLTVIER and J. SALAUN, Sjm’etr, 1994, (1 l), 949-951 Pd(0) catalysed reduction of trialkylsilylallyl esters by hydrides from HCOONa or n-BuZnC1 (p-elimina- tion) led to allysilanes as major products, under mild conditions, suggesting a new and stereoselective route to electrophilic reagents. Pd(0) was Pd(OAc),:PPh, in ratio 1:2. When Pd is exclusively positioned on the ring then hydrided substitution occurred at the a or y of the silyl group, depending on the hydride source.

35, (5), 728-733

Highly Selective Palladium Catalyzed Hydrogen Transfer from H,O-CO to the C=C Double Bond of P-Benzoylacrylic Acid G. CAVINATO, L. RONCHIN and L. TONIOLO, 3. Mol. Caral., 1994, 94, (2), 173-180 A Pd-HC1 catalytic system is very active and selective for H transfer from H,O-CO to the olefinic double bond of the unsaturated y-ketoacid PhCOCH= CHCOOH to PhCOCH,CH,COOH. High yields are obtained only when the Pd catalyst is used in combination with HCI. Pd/C also showed high activity. Addition of HCI to the olefinic double bond of the substrate gives PhCOCHzCHCICOOH, which oxida- tively adds to “reduced Pd” to form an intermediate with a Pd-[CH(COOH)CH,COPh] moiety.

Palladinm(0) Complex-Catalyzed Debro- minative Coupling of (Tribromomethy1)- and (Dibromomethy1)benzenes to Diarylacet- ylenes and 1,2-Diarylethenes S. MATAKA, G.-B. LIU and M TASHIRO, Synthesis, 1995,

Pd(0)-triphenylphosphine complex catalysed the debrominative coupling reaction of (mbromomethyl) benzenes to give diarylacetylenes or a mixture of (a- and (Z)-a,P-dibromostilbenes, depending on the substrate and the solvent used. The coupling reaction was studied using three catalytic systems: Pd(PPh,),; a combination of Pd(I1) acetate, Biphenyl phosphine and triethylamine; and Pd(PPh,),Br, and methylamine. A great acceleration in the coupling reaction was observed in N,N-dimethylacetamide, compared with that in dimethylformamide.

Hydroformylation with a Rhodium/Bulky Phosphite Modified Catalyst. Catalyst Comparison for Oct-1-ene, Cyclohexene, and Styrene A. VAN ROOY, E. N. ORJJ, P. C. J. KAh4ER and P. W. N. M. VAN LEEUWEN, Organometallics, 1995, 14, (I), 34-43 Hydroformylation of oct- 1 -me, cyclohexene and styrene was studied using Rh(CO),acac as the catalyst precursor and tris(2-tert-butyl-4-methylphenyl) phosphite (1) as the ligand at 40-1OO0C, under CO and H, pressures of 2 .444 and 2.5-50 bars, respectively, in toluene as a solvent. Very high hydroformylation rates were obtained for oct-1-ene under mild conditions. The rate-determining step is the reaction of H, with the acyl Rh complex. The Rh catalyst combined with (1) is an excellent catalyst, particularly for unsubstituted alk-1-enes under mild conditions.

Rhodium-Catalyzed Modification of Poly- (methylhydrosiloxane) into a Highly Cross- Linked Polysiloxane N . SATYANARAYANA and H. ALPER, Macromolecules,

Modification of poly(methylhydrosi1oxane) was achieved using a Rh complex catalyst, such as RhCl(PPh,), and [Rh(CO),CI], via a dehydrogena- tive coupling reaction followed by in-situ oxidation of the Si-Si bond under mild conditions. The reaction gave a thermally stable cross-linked polysiloxane.

(2), 133-135

1995,ZS, ( I ) , 281-283


New Hydroformylation Rhodium Catalysts with Dithiolate Chiral Ligands A. M. MASDEU, A. OREJON, A. RUIZ, s. CASTILLON and c. C L A V E R , ~ Mol. Catal., 1994,94, (2), 149-156 A new precursor system using Rh(1) complex catalyst with a bridge dithiolate chiral ligand: [Rh,(p- (-)-DIOS)(CO~)~],, n = 2(1) and n = 1 (2); (where (-)-DIOS is 2,3-O-isopropylidene- 1,4-dithio-~-thre- itol and cod: 1,5-cyclooctadiene), was used for asymmetric hydroformylation of styrene. System (1) gave high conversion to corresponding aldehydes (1 00% at 30 bar, 65°C) with a selectivity in 2-phenylpropanal of 64%. On addition of PPb, selectivity was further increased to 9 1 % under the same conditions.

Cis- [RhI(CO)(Ph2PCH,P(S)Ph,)]: A New Catalyst for Methanol Carbonylation M. J. BAKER, M. F. GILES, A. G . OWEN, M. J. TAYLOR and R. J. W A ? T , ~ Chem. Soc., Chem. Commun., 1995, (2),

The complexes cis-[RhI(CO)(Ph,PCH,P(S)Ph,)] was found to be 8 times more active than the classic Monsanto catalyst [RhIz(CO),]- for the carbonylation of methanol at 185°C. This catalytic system is the first promoted system effective under conditions which allow indusmally realistic rates. An X-ray crystal SUUC-

ture study of the analogue complex cis-[RhCl(CO)- (Ph2PCH2P(S)Ph2)] is reported.

Formation of 2-Alkylaminooxazoles by the Rh,(OAc),-Catalyzed Reaction of a- Diazocarbonyl Compounds in the Presence of Cyanamides

197-198

K. FUKUSHIMA and T. IBATA, Heterocycles, 1995, 40, (l), 149-154 The Rh,(OAc),-catalysed reaction of a-diazoace- tophenones with N,N-dialkylcyanamides (1) yielded the corresponding 2-(N,N-dialkylamino)-5-aryloxa- zoles in high yields and could be used as the general method for the synthesis of 2-alkylamino-5-aryloxa- zoles. Unsubstituted and monosubstitued cyanamides gave the corresponding 2-aminooxazoles in low yields. 2-(N,N-Dialkylamino-5-alkoxyoxazoles formed by the similar reaction of diazoacetates with (1) were found to be unstable upon isolation.

Rh,(OAc),-Catalysed Cycloaddition of Ethyl Diazoacetate to 1,2-Dialkoxybenzenes: a New Type of Stable Norcaradiene M. MATSUMOTO, T. SHIONO, H. MUTOH, M. AMANO and s. ARIMITSU, J. Chem. SOC., Chem. Commun., 1995, (l), 101-102 Studies of Rh,(OAc),-catalysed cycloaddition of ethyl diazoacetate to 1,2-methylenedioxybenzene yielded the corresponding cycloheptatrienes, but the reaction of 1,2-dimethoxybenzene gave a new type of stable norcaradiene (1). Treatment of (1) with tetracya- noethylene in benzene at room temperature gave exclusively the Diels-Alder adduct. The transesterification of (1) with MeONa in MeOH caused ring-opening of the cyclopropane and the double bond isomerisation to afford cycloheptatrienes in 77% yield, but the hydrolysis of (1) by NaOH gave a complex mixture.

Asymmetric Catalytic Hydrogenation of a- Ketoesters Using New Chiral Ru(II)(AMPP) Complexes F. HAFTOT, F. ASBOSSOU and A. MORTREUX, Tetrahedron: Asymmetry, 1995, 6, (l), 11-14 The reaction of the appropriate Ru precursor with amino(amido)phosphinephosphhite ligands produced the corresponding Ru-bismethylallyl complexes: Ru(AMPP)(CH,C(CH,)CH,), and biscarboxylate Ru(AMPP)(OCOR), (R = CH, or CF3) complexes. These complexes act as efficient catalyst precursors for the homogeneous asymmetric hydrogenation of a-ketoesters with enantiomeric excess up to 79 YO.

Asymmetric Hydrogenation of Olefins with Aprotic Oxygen Functionalities Catalyzed by BINAP-Ru(II) Complexes T. OHTA, T. MIYAKE, N. SEIDO, H. KUMOBAYASHI and H. T A K A Y A , ~ Org. Chem., 1995,60, (2), 357-363 Cyclic a,@-unsaturated ketones, alkylidene lactones and alkenyl ethers were hydrogenated in high enantiomeric excesses by BINAP-Ru(I1) complexes (BINAP = 2,2'-bis(dipheny1phosphino)- 1, 1'-binaph- thyl) as catalysts. These 5-membered cyclic ketones, lactones and ethers having exocyclic C=C bonds were hydrogenated in very high enantioselectivities of - 98%. With alkenyl esters and ethers, ethereal 0 is important for the enantioface differentiation. The asymmetric hydrogenation can be successfully applied to the synthesis of (R)-4-methyl-2-oxetanone, which is a useful monomer for biodegradable polymers.

A Ru Catalyzed Addition of Alkenes to Alkynes B. M. TROST, A. F. MDOLESE, T. J. J. MULLER and B. TREE TOW,^ Am. Chem. SOC., 1995,117, (2), 615-623 Thermal bimolecular addition of unactivated alkenes to unactivated alkynes was performed using several Ru complexes including (PhOCHI)(Ph3P)RuCI,, @- cymene) (Ph,P)RuCI,, (p-cymene) [(C4HP),P] RuCI, and CpRu(C0D)CI. The latter Ru complex gave the highest conversions and regioselectivities in aqueous DMF at 100°C or MeOH at reflw. Internal and terminal alkynes react. The reaction has great chemo- selectivity and control of product double bonds.

Structure and Mechanism in Aerobic Alkene Epoxidations Promoted by Ruthenium Complexes of Bis(dihydrooxazo1e) Ligands

ROWLING, E. SINN and s. WOODWARD, 3 Chem. Soc., Dalton Trans., 1995, (3), 367-376 Reaction of [RuC12(NCMe),(cod)] with bis(dihy- drooxazoles) gave [RuCl,(cod) { (S,S)-R,'C- (C=NCHRZCR210)2}] where cod = cycloocta-13- diene; R' = H, R' = CH,Ph or Pr'; R' = Me, R2 = Pr'. Mechanistic studies of the epoxidation of styrene and stilbenes in the presence of isobutyraldehyde and 0, using the Ru complexes as catalysts were performed with and without 4-ten-butylcatechol as a radical trap. The metals acted as promoters for the production of Pr'C0,H which carried out the epoxidation either directly or by the formation of 0x0-Ru species.

S. BENNETT, S. M. BROWN, G. CONOLE, M. KESSLER, S.


Ruthenium Tetroxide as a Phase Transfer Catalyst in Biphasic System and Its in situ Electrochemical Regeneration: Oxidation of Aromatic Primary Alcohol and Aldehydes s. RAJENDRAN and D. C. TRIVEDI, Synthesis, 1995, (2),

RuOl was used as a phase transfer catalyst in a biphasic system of CClr and saturated NaCl at a platinised Ti anode to regenerate spent oxidant for the oxidation of benzyl alcohol (l), benzaldehyde (2) and p- anisaldehyde (3). The pH of the system was almost neutral and therefore the oxidation was due to RuO, and not by RuO, and RuO,' . RuO, generated in the CCl, layer oxidised (1) to (2), (2) to benzoic acid and (3) to panisic acid in good yields.

Regiocontrolled Hydrosilation of a,P- Unsaturated Carbonyl Compounds Catalyzed by Hydridotetrakis(tripheny1phosphine)- rhodium(1) G. z. ZHENG and T. H. CHAN, Organometallics, 1995,14,

The hydrosilation of a,P-unsaturated carbonyl compounds catalysed by (Ph,P),RhH was found to be highly regioselective, depending on the silanes used. Diphenylsilane gave 1,2-hydrosilation, but dimethyl- phenylsilane and other monohydrosilanes gave 1,4- addition. The kinetic isotope effect of the hydrosilation reaction was examined. This catalyst gives milder reaction conditions than (Ph,P),ClRh.

153-154

(l), 70-79

FUEL CELLS Oxidation of Methane over Platinum in a Solid Proton-Conducting Electrolyte Cell v. D. BELYAEV, v . v. GALVITA, v. P. GORELOV and v. A. SOBYA", Catal. Len., 1995, 30, (1-4), 151-158 The complete oxidation of CHI on a Pt electrode-catalyst in the cell with a solid proton-conducting electrolyte of (CH, + Oz, Pt / SrCeuu2Dyooa03 / Pt, H,O + N,) was studied. The induced change in the reaction rate at anodic polarisation of a Pt electrode-catalyst was found to be more than two orders of magnitude higher than the rate of H pumping from the reaction zone through the electrolyte.

CHEMICAL TECHNOLOGY Synthesis of Palladium Impregnated Alumina Membrane for Hydrogen Separation s.-J. LEE, s.-M. YANG and s. B. PARK, J: Membrane Scz.,

A Pd impregnated A1,0, membrane was prepared directly by mixing A120, sol with a Pd precursor, followed by sonication to disperse the Pd particles uni- formly throughout the membrane. A H-selective y- Al,O, membrane containing Pd particles was formed as an intermediate layer in an asymmetric porous support. The average pore radius and surface area measured by BET were 20.8 A and 217.4 m2/g, respectively. The dispersion of P{ in the membrane is 0.3 1 and the particle size is 32 A.

1994,96, (3), 223-232

ELECTRICAL AND ELECTRONIC ENGINEERING Magneto-Optic and Optical Properties of Multilayered CoPd Films YU. v. KUDRYAVTSEV and R. GONTAZH, Fiz. Met. Metalov., 1994, 77, (6), 44-52 Magneto-optic and optical properties of multilayered Co/Pd films in various stages of modulated composition were studied at 293 K over a wide spectral region. Results showed that the value of the magneto- optic effect in a monolayer Co/Pd film l p n thick was proportional to the volume of Co concentration in the layer. Variations of this dependence occurred in the UV spectral region with decrease in the layer thickness, due to polarisation of the Pd layer position at a small distance from the Co layer and to the changes in magneto-optic parameters in very thin Co layers.

Hydrogen-Sensitive Property of Switching Device with a Pd-Si Tunnel Insulator Semiconductor Structure s. NAKAGOMI and r. YAMAMOTO, 3pn. 3 Appl. Phys.,

The effect of atmosphere on a switching device with a Pd-Si tunnel metal insulator semiconductor (MIS) structure was studied. The MIS device, Pd-insulator- (n)Si-(p')Si structure, showed negative-resistance switching properties. Work function data were obtained. O2 increased the work function of Pd while H, decreased it.

A Comparison Study of Pd/In/F'd, Pd-IdF'd, and Pd-In Ohmic Contacts to n-GaAs H. G. FU and T. s. H U m G , Solid-state Electron., 1995,

Metallurgical and electrical characteristics of layer- deposited (1) Pd/In/Pd and codeposited (2) Pd-IdPd and Pd-In ohmic contacts to n-GaAs were studied. The codeposited contacts (2) have smooth surfaces, and their minimum specific contact resistances are 3 x Rcm' after annealing at 600°C for 10 s. However, contacts (1) have rough surfaces with many hollow blisters which are explained by the local vapor- isation of In during deposition of the outermost Pd layer. The contact resistance of all (1) and (2) contacts increased with time after 400°C ageing.

1994,33, ( l l ) , 6136-6140

38, (l), 89-94

TEMPERATURE MEASUREMENT Design of RuOpBased Thermometers for the Millikelvin Temperature Range I. BAT'KO, K. FLACHBART, M. SOMORA and D. VANICKY, Cryogenics, 1995, 35, (2), 105-108 Thick Ru0,-based thick film resistors were designed as low temperature thermometers in the millikelvin temperature range. These resistors can be used as an alternative to Ge ones, and both the R-T characteristics and the sensitivities can be altered simply by changing the distance between conduction pads. The temperature dependence of the resistance of RuO, sensors at the lowest temperatures studied is described in terms of a variable-range hopping mechanism.


NEW PATENTS METALS AND ALLOYS Platinum Alloy Used for Jewellery Articles NAGAHORI CORP. British Appl. 2,279,967A A Pt alloy Containing 10-100 ppm Ce is claimed as an article of jewellery and comprises the Pt alloy, preferably containing t 99 wt.% Pt and 18, 34, 66 or 98 ppm Ce. The Pt alloy has a high degree of hardness despite its low Ce content, and still has adequate hardness even after casting. Therefore no secondary processing for increasing hardness is required.

Fine Palladium Alloy Wire

Iridium Acetylacetonate Solution Preparation

Japanese Appl. 61247,890 An aqueous mixture of Ir(1V) ion and/or Ir(IV) complex ion, a reductant such as hydrazine, sulphurous acid, or oxalic acid, etc., and alkali acetylacetonate is heated, followed by salting out Ir acetylacetonate and acetylacetone fiom the heated mixture. Ir acetylacetonate is used as a clarification catalyst for NOx and as an electronic material in organic metal ink, etc. The reaction is carried out at 70-140°C. The complex is stable in store, and is obtained in high yield.

SUMITOMO METAL MINING CO.

ELECTROCHEMISTRY NIPPON STEEL CORP. World Appl. 9412 1,833A A fine Pd alloy wire for bonding semiconductor elements is produced kom a Pd alloy with S 0.0003 wt.% of each of Ca, Al, Cr and Si, 0.001-0.01 wt.% Ir, and for Ion Water Generator ifnecessary at leist either 0:001-2 wt.% AU of purity 2 99.99 % or 0.001-5.0 wt.% Ag of similar purity, the balance being Pd. The wire has secured junc- tion reliability and its configuration is improved.

Nickel-Free White Gold Alloys for Jewellery HANDY & HARMAN US. Patent 5,372,779 A white gold alloy composition for jewellery comprises in wt.%: 35-50 Au, 25-63 Ag, 0.1-7 Zn andlor Ge as whitener, and 5 Pd. The liquidus temperature is S 1950OF. The alloys are substantially free of Ni, and thus non-allergenic. They display a favourable white hue, low casting temperature, good workabil- ity, sufficient hardness and tarnishing resistance.

Production of Superconductor CHODENDO HATSUDEN KANREN KIM ZAIRYO

Japanese Appl. 6/25 1,649 A superconductor member is produced by forming an oxide superconductor layer onto a Ag-Pt substrate alloy containing 0.1-50 wt.% Pt group metal. The superconductor body may be La, .AE.CuO,, REBa,Cu,O,-k, etc., AE3 is at least one of Ba, Sr, Ca, x = 0.024.08, RE is one of Y, Sc, La, etc., and the superconductor layer can be produced by sputtering or CVD. The superconductor has a high critical point, good heat stability and is highly reproducible.

CHEMICAL COMPOUNDS Double Oxide Preparation SANTOKU KINZOKU KOGYO K.K.

Japanese Appl. 61246,155 A new double oxide containing Ce oxide also contains 0.01-10.0 wt.% of Pt group metal, such as Pd, andlor 0.01-10.0 wt.% of transition metal oxide. A solution containing Ce ions, Pt group metal and/or transition metal is mixed with an aqueous solution containing NH,, NH,HCO, or oxalic acid, followed by firing the precipitates at =- 250°C. The oxide can absorb and discharge t 100 pmoYg 0, below 300°C. The oxide can be used for a waste gas purification catalyst and in other ceramics.

MATSUSHITA DENKI SANGYO K.K. Japanese Appl. 61228,783

The electrode has base metal coated with Al oxide .or Ti oxide, and a Pt alloy film coated on the oxide film. The electrode is used for an alkali ion H,O generator. It has a large surface area and good adhesiveness.

Electrode Coated with Iridium Oxide NIPPON STEEL CORP. Japanese Appl. 61235,097 The non-soluble electrode comprises a metal base optionally with a layer of valve metal, which includes Ti and Zr, an Ir oxide layer and a metallic Ir layer. The Ir oxide layer and the metallic Ir layer are formed in turn to obtain an uppermost layer of Ir oxide; each coating layer is I 20 pn thick. The Ir oxide layer preferably accounts for 67-99% of the total film thickness, and the metallic Ir layer for 1-33% of the total film thickness. The film is deposited at S 700°C. The coating layer adheres tightly to the metal base.

Electrodes for Water Generation TOHO TECH. SERVICE CO. LTD.

Japanese Appl. 6/254,5 64 Electrodes used in an electrolytic tank of an electrolytic H,O generator comprise a thin plate of metal formed by applying Pt burning to a flat plate of Ti. The thin plate of metal is provided along the shape of the electrode-facing-surface of an insulating base. Pt is applied to the facing surface of each electrode along the surface of the cylindrical insulating base. There is no metal elution even if the polarity is inverted.

Electrolysis Cell Production

A cell is produced by applying a Pt paste onto both sides of a solid electrolyte layer to form an electrode, applying Pt wire nets onto the solid electrolyte layer, followed by heat treatment for sintering. The solid electrolyte layer is Y,O,-stabilised Zr0, and the Pt paste is 70% Pt and balance binder. The electrode has good electroconductivity and the solid electrolyte has good resistance to deterioration. The current density distribution in the solid electrolyte is uniform.

MITSUBISHI JUKOGYO K.K. Japanese Appl. 6/260,18 1


Electrode for Alkali Ion Water Generator MATSUSHITA DENKI SANGYO K.K.

ELECTRODEPOSITION AND Palladium Coating Solution SURFACE COATINGS VICTORIA K.K. Japanese Appl. 61264,28 1

Pd coating solution contains a primary Pd oxide compound at 5-30 gll as Pd metal, and a weak organic acid as conductive salt at 30-500 gll. An object is immersed into the Pd coating solution to acquire an electrocoating at 10-50°C and 0.1-3 Ndm'. The plating solution contains Pd acetate 10 gl1 as metallic Pd, oxalic acid 150 gll and Na sulphite, and has pH 3. Plating is performed at 1.5 V, 0.5 Ndm' for 30 min. No coating separation was observed after bend tests.

Plated Ornament Colnponent Japanese Appl. 6/264,2 8 2 NAU CHEM, YG,

An ornament component comprises a conductive substrate coated by a Au-Pt alloy layer containing 0.001-30 wt.% Pt and balance Au. In an example, the plating bath acid and N~ citrate, at pH 4.0. A brass sheet electrolysed in the bath at 1 ,O a pt electrode acquired

a mirror gloss face. The component does not harm

Electrolytic Palladium Coating Solution ATOTECH DEUT. G.m.b.H. European Appl. 619,386A A Pd electroplating solution contains Pd sulphate andlor sulphamate, complexing agents and hetero- cyclics, such as 2,3-bis-(2-pyridyl)-pyazine, etc., and is used for electroplating electrically conducting substrates with Pd or Pd alloy, in jewellery, watches and printed circuit boards. The addition of a heterocyclic compound allows the production of high-gloss, light Pd coatings which are very ductile and free from haze.

Palladium-Coated Copper-Based Lead Frmes HERAEUS G.m.b.H. European Appz. 621&33A A lead frame for ICs comprises a metallic base with at least two coating layers, the Outer being Pd and the inner layer Ni-P or Cu-Sn. The Pd layer is 0.01-5

before and especially after ageing is obtained.

10 gll A ~ , 0.3 8/1 pt,

WY Preferably 0.1 )Im thick. Good solderabib', both a coating layer 7.2 pm thick of hardness Hv 132 with

Electroless Metallisation of Optical Fibre AMERICAN TELEPHONE & TELEGRAPH CO.

European Appl. 623,565A Optical fibres are electrolessly metallised by treating with an aqueous sensitising solution of SnF,, then with an activating Pd(1I) solution to deposit a catalytic layer on the sensitised surface, and finally depositing Ni by immersion. The process is reliable and achieves uniform reproducible Ni plating on SiO, fibres.

Coating Metal Surfaces with Palladium ATOTECH DEUT c.m.b.H. World Appl. 94126,954A Layers of Pd are deposited on a metal surface from a formaldehyde-free chemical plating bath containing a Pd salt, N-containing complexing agents and formic acid or formic acid derivatives at pH > 4. The process allows the deposition of permanently glossy, bright, ductile layers of highly pure Pd on metal substrates, at < 5 pmih.

Electroless Deposition MONSANTO CO. US. Patent 5,348,574 An electroless deposition-catalysing film-forming solution comprises: (a) 0.1-15 wt.% polyamic acid, (b) 0.1-151100 pts. polyamic acid noble metal of Pt, Pd, Rh, Ir, Ru, Ag or Au, and (c) 60-95 wt.% aprotic solvent from acetone, etc., and mixtures with H,O, and (d) 0-10 wt.% anionic or non-ionic surfactant. The solutions provide coherent polyamic acid films which can be imidised to provide tough and adhesive polyimide films for electroless deposition.

Thick Crack-Free Ruthenium Coating JAPAN ENERGY K.K. Japanese Appl. 61256,988 Coating with Ru comprises the use of a coating solution containing a complex of Ru with N and S acid and blowing an 0,-containing gas into the solution. The 0, blow assures the formation of a crack-free thick Ru coating layer. A mixture of Ru chloride and sulphamic acid with HSO, acid and other additives was used to give crack-free 7.6 pm thick coatings.

skin and there was no discoloration after 6 days.

APPARATUS AND TECHNIQUE Iridium Oxide Film Manufacture

Ir oxide film is manufactured by sputtering a target of Ir oxide disposed in a vessel with inert gas ions irradiated from an ion gun at a pressure of 1 x 10 to 1 x 10 ' Torr by an ion beam sputtering process. The technique is used to coat the surface of electrodes giving an insoluble anode for electroless plating; good coating adherence is obtained.

Hydrogen Separation Membrane Production NOK CORP. Japanese Appl. 612 5 4,3 6 1 The membrane is prepared by coating porous hollow ceramic yarn with pAl,O, by a sol-gel method, spray- ing with Pd(NO,),-AgNO, mixed solution, which is thermally decomposed to form Pd-Ag alloy. The membrane is chemically and thermally resistant. In an example, porous hollow ceramic yarn Al,O, is sprayed with a nitrate solution containing a Pd : Ag ratio of 60 : 40 and is thermally decomposed with HL to form a ceramic membrane for H, separation with permeation coefficient for H, = 5 x 10 ' mollm's Pa.

NIPPON STEEL CORP. Japanese Appl. 61235,065

HETEROGENEOUS CATALYSIS Ether Alcohol Production KAO COW. European Appl. 616,994A Ether alcohols, which are useful as perfumes or for perfume production, are produced by subjecting a cyclic ketal to hydrogenolysis in the presence of a catalyst containing 50-100 wt.% Pd based on the total active catalytic component present and further containing 0-50 wt.% metal(s) selected from Ru, Rh, Pt andor Ni, supported on C, Al,O,, Si02 and zeolite. The ether alcohols can be produced easily at low cost and in high yield. The process does not require a diol solvent and is highly efficient.


Plated Ornament Component NAU CHEM. YG. Japanese Appl. 6/264,2 8 2 An ornament component comprises a conductive substrate coated by a Au-Pt alloy layer containing 0.001-30 wt.% Pt and balance Au. In an example, the plating bath contained 10 g/l Au, 0.3 g/1 Pt, citric acid and Na citrate, at pH 4.0. A brass sheet electrolysed in the bath at 1 .O A/&' using a Pt counter electrode acquired a coating layer 7.2 pm thick of hardness Hv 132 with a mirror gloss face. The component does not harm skin and there was no discoloration after 6 days.

Hydrogenation and Isomerisation of Amines AIR PROD. & CHEM. INC. European Appl. 61 8,188A The catalytic hydrogenation and isomerisation of aromatic amines to their ring hydrogenated counterparts is made with high selectivity at low pressure and with good reaction rates, by contacting the aromatic amine with H, in the presence of a catalyst comprising a mixture of Co and Rh, Ru, Pd and/or Pt. The process is useful for the production of 4,4’-methylene-di(cyclo- hexylamine), the trans,trans-isomer of which can be used to produce polyamine fibres and epoxy additives.

Hydrogen Peroxide Production MITSUBISHI GAS CHEM. CO. INC.

European Appl. 621,235A H,O, is produced by reacting Oz and H, in the presence of a Sn-modified Pt group metal catalyst on a carrier. The carrier, which has solid acidity, is 21-0, or AI,O, supporting H,SO, on a composite oxide of Mo and Zr or Sn and Si or a compound of Sn and Zr or the H form of mordenite or MFI-type zeolites. The reaction medium is H 2 0 containing an H,O, sta- biliser, and the reaction conditions are 0-50°C and pressure 3-1 50 kg/cm’. The reaction medium may be free of halogen ions and acid, thus alleviating disso- lution of the catalyst metal and reactor corrosion.

Preparation of Diacetoxybutene MITSUBISHI KASEI cow. European Appl. 625,503A Diacetoxybutene (1) is prepared by reacting butadi- ene, acetic acid and 0, in the presence of Pd based catalyst, followed by continuous two-stage distillation in two distillation towers and by thin-film evapora- tion. (1) is recovered from the top of the second tower, and the material containing (1) from the bottom of the first tower is recycled into the second tower. The Pd based catalyst contains Pd metal or Pd salt singly or in combination with Bi, Se, Sb, Cu, etc., and is supported on SO,, A120, or activated C. The process allows recovery of high purity diacetoxybutene in high yield. (1) is a raw material for the production of 1,4- butanediol and tetrahydrofuran, etc.

Treatment of Waste Water SOLVAY D E W G.m.b.H. wort’d Appl. 94120,423A Waste H 2 0 containing organic and optionally inorganic compounds with adsorbable organo-halogen compounds, especially from epichlorohydrin production, is treated in the presence of H, by a supported Pt group metal catalyst, preferably Pd, Pt, Ir or Rh, supported on SO,, Al,O,, MgO, ZrO,, etc., prepared by the sougel process. The waste H,O, having pH 3-10 (4-6), is fed into a reactor containing the high activity catalyst, and treated at 580°C and 1-10 bars with H,.

Removing Nitrogen Oxides &om Exhaust Gas NIPPON SHOKUBAl co. LTD. World Appl. 94125,143A A method of removing NOx contained in an exhaust gas comprises contacting the gas in an oxidising atmosphere with a catalyst of 0.1-30 g/l-catalyst of at least one of Pt, Pd, Rh and Ru metals or their compounds, and 1-80 g/l-catalyst of Li, K, Na, Rb, Ce, Be, Mg, Ca, Sr, and Ba, on a refractory inorganic oxide.

Conversion of 1 - 4 C Hydrocarbons to Olefins

World Appl. 94127,722A New supported Ru catalyst for the preparation of lower hydrocarbons containing a double bond and C, is produced by the conversion of 1-4C hydrocarbons or purified natural gas. The catalysts contain 0.25-5 wt.% metal in the catalyst of RuCl,(PPh,),,

IrCl(CO)(PPh,),, Pd(PPh3)4, Pt(PPh,),, RuCl,.xH,O, RhCl,.xH,O, etc., supported on a- or y-Al,O,, SiOr and Si02-Al,0,, Y zeolite, etc. The conversion is carried out at 500-980°C and at a pressure of 1-10 atm.

Dehydrogenation Catalyst CHINA PETRO CHEM. cow. US. Patent 5,358,920 A long-life supported catalyst for use in dehydro- genating saturated hydrocarbons comprises, in wt.%: (a) 0.01-2.0 Pt; (b) 0.01-5.0 Sn; (c) 0.01-5.0 Na; and (d) the remainder of large pore diameter ~-Al,0, support having a dual pore diameter distribution such that at least 40% of the total pore volume has pores of diameter 1000-10,000 A. The catalyst is used to dehydrogenate (6-1 6C) linear paraffins to prepare linear mono-olefins. The catalyst has a high stability and can be used under severe operating conditions, such as high temperature and low pressure and does not need sulphiding treatment before use.

Method of Controlling Hydrosilylation DOW CORNING COW. US. Patent 5,359,111 Hydrosilylation in a reaction mixture is controlled by adjusting the concentration of 0, in solution, relative to any Pt catalyst in the reaction mixture, as Pt metalkupport, Pt compound or complex. Hydrosilyl- ation is also controlled by reacting a Si hydride with olefinically unsaturated alkenyl compounds selected from 4-8C cycloalkenyl compounds, linear 2-30C alkenyl compounds, and branched 4-30C alkenyl compounds in the presence of catalyst.

Tert. Butanol Production TEXACO CHEM. CO. US. Patent 5,359,130 A solvent solution of a tert-butyl hydroperoxide (TBHP) charge stock is decomposed by a mixed Pd and Pt/Al,O, hydroperoxide decomposition catalyst; tert-butanol is recovered from the products of the decomposition reaction. The reaction is performed at 25-250°C and 0-1000 psig and the catalyst contains 0.1-5 wt.% Pd and 0.1-5 wt.% Pt in ratio Pt:Pd of 0.1-10: 1. The TBHP may be dissolved in an isobutane-tert-butanol mixture, at 0-10,000 psig. Conver- sion rates and selectivity for ten-butanol are high.

Synthesis of Methyl Tert.-Butyl Ether TEXACO CHEM. CO. US. Patent 5,364,981 One-step synthesis of an alkyl tert-alkyl ether comprises reacting a 1-6C primary alcohol with a P l O C tertiary alcohol at molar ratio 10: 1-1 : 10 in the presence of a p-zeolite modified with metals from Group VIII, also containing a halogen or Group IB metal, at 20-250°C and 1000 psi pressure. The catalyst is reduced in a stream of H, at 100-600°C. The Pt- Pd-modified zeolite catalyst exhibits high activity.

KOREA RES. MST. CHEM. TECHNOL.

RuCL(CO)2(PPh,)z, R~J(C0)izj RhCl(CO)(PPhdz,


Two Stage Reforming of Naphtha EXXON RES. & ENG. CO. US. Patent 5,368,720 A two-stage process for improving the octane quality of a naphtha feedstock containing a mixture of paraffins, aromatics and naphthenes involves a reforming first stage of fixed-bed reforming zones containing a catalyst of 0.1-0.7 wt.% Pt, 0.1-0.7 wt.% Ir and 0.02-0.4 wt.% Sn on an inorganic oxide support, and a second stage of moving-bed reforming zones with a Pt containing catalyst. The catalyst is continuously regenerated and recycled. Catalysts have high activity and produce high yields of 5C+ reformate.

Diesel Exhaust Purification Catalyst TOYOTA JIDOSHA K.K. Japanese Appl. 611 82,204 An exhaust gas purification catalyst for diesel engines comprises a honeycomb support having axially parallel paths and a core section, and plugged-in che- quers-like patterns at the outlet and inlet. A Pd catalyst is supported on the cross flow section while a Pt catalyst is supported on the straight flow section. The catalyst is used for a diesel engine to burn HC, CO

Production of Dimethylol Alkanoic Acids KOEI CHEM. IND. co. LTD. Japanese Appl. 61192,169 Dimethylol alkanoic acids (1) useful as raw materials for polyurethane and epoxy resin preparation, were prepared by oxidising uimethylol alkane with 0,-containing gas in aqueous solvent using Pd andor k catalyst, such as 5 wt.% PdlC, while keeping the system at pH 7-12. 0,-containing gas was bubbled through, at O-lOO"C, preferably 20-70°C. (1) can be produced safely by a short process from easily available materials.

Purification of Exhaust Gas of Diesel Engine CATALERIND. CO. LTD. Japanese Appl. 61198,181 A catalytic system that purifies exhaust gas from diesel engines, consists of a base material carrying a catalyst layer on its surface, a chamber containing PtIAl,O, upstream in the exhaust gas flow and another chamber containing PdAlzO,-Si0, downstream. Altogether, three catalysts are installed. This method prevents sulphate discharge, generation of white smoke, and generation of NO,, and decomposes NOx efficiently.

and soluble organic fraction contained in exhaust gas. The catalvst retains low Dressure loss and reduces the Decomposition Of Nitrous Oxide release of particulates over a large temperature range.

Catalyst for Purifying Exhaust Gas NISSAN MOTOR CO. LTD.

Japanese Appls. 61182,213 and 61182,215 Catalysts for purifying exhaust gas from cars comprise a honeycomb support, and either a first layer of Al,O, containing Pt, Pd andor Rh and a second layer of zeolite containing Cu, Co, Ni, etc.; or a first layer of AlzO, with Pd or Rh, a second layer comprising metal oxide supporting Pt and a third layer of zeolite. The catalysts efficiently purify HC, CO or NOx from car 1.C.E; they have high NOx activity at low temperatures from the theoretical air:fuel ratio to the lean region, and good fuel consumption.

Alicyclic Diol Preparation NEW JAPAN CHEM. CO. LTD. Japanese Appl. 61184,032 Alicyclic diols (1) are prepared in high purity and yield by the catalytic hydrogenation of aromatic diols in the presence of a catalyst comprising one or more Ru, Pd and Rh on carriers, such as oxides of Ca, Mg, Al, Si, Ti, Cr orland Zr. In an example, the catalyst is Ru or Pd supported on A1,0, or SiO, preferably in the ratio of meta1:carrier of 0.5-5 wt.%. The hydrogenation is performed at 6O-17OoC for Ru or Rh, or at 12O-220"C for Pd under 30-200 kglcm' for 1-7 h.

Preparation of Hydrogen Peroxide MITSUBISHI GAS CHEM. CO. INC.

Japanese Appl. 611 9 1,804 H,O, is prepared in high concentration by reacting 0, and H2 catalytically in a reaction medium using a Pt group metal catalyst, such as Pt or Pd on an organic halogen compound (not a F containing compound) on a solid acid support with acidity function < -3 or a solid acid support with very strong acidity. The support preferably contains an insoluble heteropolyacid, of phospho-wolhmic acid or tungstosilicic acid, cation exchanged with K or Cs.

SAKAI KAGAKU KOGYO K.K. Japanesefippl. 61198,187 An A1,0, catalyst carrier has two catalytic metals one being at least one of Ru, Rh and Ir, and the other at least one of Cu, Co and Fe. The catalyst decomposes N,O in NOx efficiently at low temperature and in the presence of H,O vapour.

Exhaust Gas Denitration Process SUMITOMO METALMINING CO.

Japanese Appl. 61210,137 Exhaust gas is firstly contacted with a catalyst, which is active at higher temperature, containing 0.01-5 wt.% Pt and 0.01-10 wt.% of at least one of Fe, Co, Cu and Mn, and secondly is contacted with 0.01-5 wt.% Pt catalyst which is active at lower temperature. The process operates over a wide temperature range.

Denitrification Catalyst for NOx Removal SUMITOMO METAL MINING CO.

Japanese Appl, 61210,171 NOx in exhaust gas is contacted with a denitrification catalyst containing 0.05-5% Pt on a support of specific surface area at least 200 m'lg, containing B,O,, SiO, and A1,0,, for purification in the presence of hydrocarbons and oxidative atmospheres. NOx is removed efficiently, even under excessive 0, atmospheres, using this catalyst.

Purification Catalyst for Exhaust Gas DAIHATSU MOTOR CO. LTD.

Japanese Appls. 61210,174-75 A Pt group metal solution containing Pt, Pd, Rh, Ir or Ru at pH 4-10 is impregnated or adsorbed on perovskite oxide of Ln, .A.MO, where Ln is a rare earth metal, A = alkali earth metal or Ce, M = transition metal, x = 0-1, and a thermal resistance oxide of composition Cel.,SiyO,, y = 0-1, dried and burned to give an exhaust gas purification catalyst. With this catalyst, HC, CO and NOx in exhaust gas is removed efficiently even at > 900°C.


Cleaning of Exhaust Gas Containing NO S A W KAGAKU KOGYO K.K.

Japanese Appls. 612 18,232-33 Cleaning exhaust gas containing NO comprises contacting gas by a catalyst supporting Pt, Pd, Rh, Os, Ir, Ru or Re, and additionally Cu, Co, Fe, etc., in the presence of a reducing gas at 200400°C and space velocity of 500-100,000. The carrier is treated with F by dipping zeolite, SiO,, Al,O,, into aqueous HF, K ammonium fluoride, etc., washing with H,O and calcining at 300400°C. This method is useful for fur- naces which burn city garbage and mud from treating sewage, by catalytic decomposition of NO-containing gas in high efficiency, even at low temperature.

Removing NOx from Exhaust Gas AGENCY OF IND. SCI. &TECH.

Japanese Appl. 61218,236 Removing NOx in exhaust gas containing an excess amount of O2 comprises contacting exhaust gas with a catalyst of main component Pt in the presence of a cyclic HC having a C=C bond, such as cyclopentane, MCP, benzene, toluene, etc. The catalyst is prepared by dipping a carrier, such SiO,, Alz03, Y-zeolite, etc., into an aqueous solution of H2PtC15, Pt(N0,)2(NH,)2, etc. The gas is contacted at 150-300°C and space velocity 1000-7000/h. The process removes NOx from gasoline or diesel-engine vehicles, at low temperature.

Treatment of Exhaust Gas MITSUBISHI JUKOGYO K.K. Japanese Appl. 61226,053 CO, HC and NOx are removed from exhaust gas by a Rh-containing catalyst and a Pt-containing catalyst arranged in series at the inlet and outlet sides, respectively. NOx, CO and HC are removed, even in excess 0, at 300-700°C. In an example, gas containing 400 ppm NO, 1000 ppm CO, 1000 ppm C,H,, 340 ppm C,H,, 8% O,, 10% H,O and 10% CO, was contacted with RhlA1,0, and Pt/AI20, arranged in series at 350°C. 100% HC and 45% NOx were removed.

Catalyst for High Temperature Combustion KOBE STEEL LTD. Japanese Appl. 61226,099 A composite catalyst for high temperature combustion includes a Pd-based catalyst supported on a heat- resistant honeycomb base at the air-fuel mixture inlet. A second Pt-based catalyst is downstream and a Mn- based catalyst is further downstream. The catalyst is used in equipment for catalytic combustion of fuel gas-air mixtures at high temperatures. The first catalyst has highest activity for CH,; the second catalyst depresses excess reaction and the third catalyst has high temperature heat resistance.

Catalyst for Purifying Exhaust Gas MATSUDA K.K. Japanese Appl. 61226,104 An Ir-containing noble metal active seed is supported on a metal-containing silicate in a catalyst, and is prepared from Ir salt, noble metal salt and organic binder. The boiling point of the Ir salt solvent is similar to the boiling point of H,O. The metals are simultaneously deposited on the silicate and provide a uniform and dispersibility-enriched active seed-supporting state, enhancing NOx purification and heat resistance.

Catalyst for Exhaust Clean-up NIPPON GLASS co. LTD. Japanese Appl. 61233,9 18 Highly durable catalyst is prepared by coating a mono- lith carrier with a catalyst layer that reduces CO, HC and NOx. The catalyst layer contains particulates formed by carrying Pt, Pd and Rh on a heat resistant inorganic oxide, as a whole layer, and 2-10 wt.% Pd in a depth less than half the thickness of the catalyst layer. Catalyst particulates carrying Rh are exposed on the surface of the catalyst layer.

Catalysts for NOx Decomposition MATSUDA K.K. Japanese Appl. 61238,170 A catalyst carrier is coated with a silicate-containing catalyst of Pt group metal such as Pt, Ir and Rh, by a wash coating method, followed by drymg, sintering and thermally treating in inert gas at 500°C. The catalysts decompose NOx in the exhaust gas of lean burn engines. Pt group metal catalysts supported on zeolite have high NOx reduction capacity.

Preparation of 1,P-Butanediol MITSUBISHI KASEI CORP. Japanese Appl. 61239,778 1,4-butanediol is prepared in high selectivity by the catalytic hydrogenation of maleic anhydride, maleic acid, succinic anhydride, etc., in the presence of a supported Pt group metal and Sn catalyst, and an alkali (earth) metal compound or a N base compound. The method gives little tetrahydrofuran by-product.

Converter for Gas Engine Exhaust purification OSAKA GAS CO. LTD. Japanese Appl. 61246,159 Pt, Rh, Pd and Ce are contained in a wash coated layer coated on a honeycomb support. The wash coat contains Pt 2 1 gll, Rh 2 0.2 gll, I’d 2 2 g/l, and Ce Z 5 gll. A gas engine uses CH, as fuel and has a ydetec- tion system for the air:fuel ratio, mounted upstream of the Rh catalytic converter to apply feedback control to the engine intake or the fuel supply.

Preparation of Platinum Alloy Catalyst TANAKA KIKWZOKU KOGYO K.K.

Japanese Appl. 61246,161 The preparation comprises supporting Pt and an alloy containing metals except Pt on a C support. The Pt and metals are alloyed at a high temperature, cooled, stood in an atmosphere containing 0.01-5 wt.% 02, followed by removal of the Pt and metals from the N, atmosphere to the air. The Pt alloy catalyst has high activity, a high surface area and gradually generates an oxidation reaction to burn a non-C support.

Denitration Apparatus for Reducing NOx SUZUKI KINZOKU KOGYO K.K.

Japanese Appl. 61254,349 A denitration apparatus comprises a wire net of heat resisting metal wire plated with Pt placed on piping through which gas is exhausted from combustion apparatus, I.C.E., gas turbines, etc. It is arranged verti- cally or in parallel. The wire may be steel, Ni, Cu, Ti, etc. It is plated with Pd, Pt-Pd, Pt-Rh or Pt-Pd-Rh alloys. The N-compound content in the combustion gas is reduced. The apparatus has thermal resistance and durability, regardless of the 0, content.


Catalyst for Removing Organic Halogen SUMKOMO METAL MINING CO.

Japanese Appl. 61254,399 A decomposition catalyser which contains 0.1-5 wt.% Pt or Pt-oxide is supported on a 0.5-5 wt.% H3P0,- containing ZrO, camer. Organic halogen compounds are removed from HzO and air by contact with this catalyser. The catalyst is stable to HC1 and HF which are generated by the decomposition of organic halogen Compounds, even in high concentration.

Hydroxylation of Aromatic Compounds TOSOH COW. Japanese Appls. 61256,24142 Hydroxylated aromatic compounds (l), especially phenols, are prepared by reacting aromatic compounds with a mixture of 0, and H, in the presence of a V-P complex oxide, such as vanadyl phosphate or divanadyl pyrophosphate, etc., and a catalyst of Pt, Pd, Rh, or Ru, preferably Pd and Pt, used in a ratio of 0.01-20 wt.% (calculated as metal) to total catalyst weight, on a carrier. The reaction is at normal temperature to - 200°C and normal to 200 kglcm' pressure. (1) are useful intermediates of aniline, bisphenols, alkylphe- nols and phenol resin.

Platinum Loaded Catalyst for Hydrosilylation

Japanese Appl. 61262,076 A new Pt-loaded catalyst used for hydrosilylation of olefins comprises an A1,03 support of 0.1-10 m'lg specific surface area loadedwith 0.1-10 wt.% Pt. The catalyst is used to produce silicone resin or in the cross-linking reaction of silicone rubber. The catalyst is easy to contact with the highly viscous reaction mixture and provides a higher catalytic activity.

Heat Resistant Catalyst for Combustion TONEN K.K. 'Japanese Appl. 61262,077 A heat resistant inorganic support containing 2.5-25% SiO,, Al,O,, etc., of specific surface area after burning at 1200°C in air of 50 m2/g, is coated with 0.1-5% Pd or PdlTi, Mg or Mn (0.08-1%, TilPd = 5-30 wt.%) to form a catalyst for combustion. A thermally resistant and highly active catalyst is obtained.

Catalyst for Purifying Exhaust Gas NISSAN MOTOR co. LTD. 'Japanese Appl. 61262,088 Catalyst for purlfylng exhaust gas containing excess 0, has a honeycomb first layer based on active ALO, containing a Pt group metal such as Pt, Pd and Rh, a second layer of Al,O, without noble metals, and a third layer on top made of Cu or Co ion exchanged zeolite. This three-layered catalyst shows high cleaning capacity for the exhaust gas of lean burn engines.

TANAKA KIKINZOKU KOGYO K.K.

Dechlorination of Chlorinated Polycyclic Aromatic Compounds BAYER A.G. German Appl. 4,310,704 Chlorinated, optionally 0-containing polycyclic aromatic compounds are dechlorinated in a continuous reaction with H, at 27&450"C in the spray phase using a fixed-bed Pdspinel catalyst. The process gives quan- titative conversion and disposes of polychlorobiphenyls. The catalyst has good selectivity and can be applied to a wide range of different starting materials.

Aromatic Amine and Diazonium Salt Preparation HOECHST A.G. German Appl. 4,316,923 Aromatic amines (1) are prepared by reducing the corresponding nitro compound with phosphorus acid, which is a by-product of organic acid chloride preparation from organic acids and PCl,, in the presence of a heterogeneous Pd catalyst. Halogenated aromatic diazonium salts (2) are also prepared by reacting the solution obtained with excess acid and aqueous NaNO, solution at -10 to 15°C. (1) andor (2) are useful as diazo copying precursors andor intermediates in the preparation of active substances, polymers and/or dyes&. The process is selective and gives high yields. It also has ecological advantages, since it removes the need for energy-intensive purification.

Catalyst for Removing Particulates from Diesel Exhaust Gases WKONG LTD. German Appl. 4,410,353 A catalyst for the removal of particulates from diesel engine exhaust gases is produced by impregnating the supported coated filter with a colloidal Pt group metal solution followed by heating the product at high temperature. The colloidal Pt group metal solution is prepared by treating a Pt group metal salt with an aqueous polymer solution and a reducing agent. The catalysts promote combustion of particulates at lower temperature so reducing SO3 formation.

Stable Catalyst Filter for Particle Removal from Diesel Engine Exhaust Gas W K O N G LTD. German Appl. 4,414,625 Catalyst for removing particles from diesel vehicle exhaust gas has a support of Al phosphate or P-doped Al,O,, which is on the surface of a heat-resistant filter and is impregnated with Pt, Pd andor Rh. The catalyst is stable at high temperature, is effective for long periods and is not deactivated by SO,. The supports also reduce the regeneration temperature.

HOMOGENEOUS CATALYSIS Oxidising and Decomposing Waste Liquid DAIDO TOKUSHUKO K.K. Japanese Appl. 61269,67 1 A catalyst is prepared by forming a Au plating layer onto the surface of a stainless steel net and laminat- ing a Pd layer onto the Au by semi-lustre Pd plating or Pd black plating. The catalyst is used to treat waste liquid and particularly HzO containing hydrazine. It is catalytically stable, has good adhesion to the substrate and high corrosion resistance to chemicals.

Hydrogenation Catalyst BASF A.G. European Appl. 62 0,042A An hydrogenation catalyst, useful for the preparation of hydroxyl-ammonium salt from NO with H,, is prepared by treating Pt metal salt with finely-divided S followed by reduction to metallic Pt. The production is simplified, the amount of waste product is reduced and the use of easily decomposed and toxic substances which cause partial poisoning is avoided.


Asymmetric Hydrogenation of Furoimidazole Derivatives LONZA LTD. World Appl. 94124,137A Asymmetric hydrogenation of furoirnidazole derivatives to the corresponding diastereomeric dihydro- furoimidazole derivatives (l), is carried out by reaction with H2 in the presence of a homogeneous catalyst obtained by reaction of a Rh complex with a chiral ferrocenylphosphine ligand. Derivatives (1) are intermediates used in the preparation of the vitamin (+)- biotin, which is used for treating dermatosis, or as an animal feed additive. The process has very good diastereo-selectivity with good yield.

Synthesis of Aromatic Diamino-Diols DOW CHEM. CO. US. Patent 5,360,932 Synthesis of aromatic diamino-diols (1) comprises contacting an aromatic halo-dinitrodiol compound (2) with excess Hz in the presence of a noble metal hydrogenation catalyst, preferably containing Pd, an aqueous solvent, 2 moles of H halidelmole of (2) and an additional amount sufficient to provide a 0.754 molar solution in the aqueous solvent. (1) are useful as intermediates in the synthesis of dyes or pharma- ceuticals, or as photographic developers, etc. The process eliminates or minimises organic solvents and produces an aqueous waste stream containing only hydrogen halide ions.

Aromatic Carbonate Manufacture IDEMITSU KOSAN CO. LTD. Japanese Appl. 6121 1,750 The manufacture of an aromatic carbonate comprises reacting an aromatic hydroxyl compound, CO and 0, in the presence of a Pd compound catalyst, such as PdCl,, Pd(OAc), and Pd(NO&, a mono- or divalent Cu compound and an NH, halide compound. This one-step manufacture method gives aromatic carbonates in high yield at a high conversion rate without using halogen-containing solvents.

Production of Alkadienols MITSUBISHI KASEI COW. German Appl. 4,410,746 Alkadienols, used to prepare octanol and its esters, are produced from conjugated alkadienes and H 2 0 in the presence of COz using a Pd compound and a free phosphine compound, such as triarylphosphine, with at least one aryl group having a substituent in an ortho position, in the reaction solution, as catalyst. The reaction is performed at room temperature to 1 80°C, and a pressure of 200 kg/cm2. Octa-2,7-dien-l-o1 is produced in improved yield and selectivity.

FUEL CELLS Phosphoric Acid Fuel Battery Stack FUJI ELECTRIC CO. LTD. Japanese Appl. 61260,207 A phosphoric acid fuel battery stack incorporates Pt in the stack top and bottom layers so that CO present in fuel is absorbed by Pt. The primarily Pt content of the catalyser layers is increased to allow H reduction. CO in the fuel is absorbed by the Pt alloy catalyser, so preventing poisoning of the battery contents. Output is increased without increasing the cost.

Hydrogen and Deuterium Occlusion by Hydrogen Storage Metal TECHNOVA K.K. Japanese Appl. 61287,786 The process involves using a closed type electrolytic apparatus with a gas diffusion electrode, such as a Pd anode used in a fuel cell. The electrolytic apparatus contains porous film, an anode of Hz storage metal, a Pt cathode and an electrolyte of 1 M LiOH containing thiowa, etc. A high occlusion gasmetal atomic ratio of > 0.97 for H2, and > 0.9 for D2 are obtained and this process is expected to be used as a fuel cell.

Electrode for Solid Electrolyte Fuel Cells JAPAN STORAGE BAlTERY CO. LTD.

Japanese Appl. 61290,789 The electrode comprises an Ir electrode formed on an 0-ion contactive solid electrolyte base by the metal organic chemical vapour deposition method. Ir acetyl acetonate may be used as a starting material. The electrode is used for solid electrolyte fuel cells.

CHEMICAL TECHNOLOGY Hydrogen Storage Material NIPPON TELEGRAPH & TELEPHONE COW.

Japanese Appl. 61256,986 Production of H2 storing material for inducing nuclear fusion uses a solution containing H ions or heavy H ions, and Pd ions; imposing a H generating voltage on the anode and cathode to deposit Pd and occlud- ing H or heavy H on the cathode. By this method, a nuclear fusion reaction is induced between H isomers. Since Pd is deposited in a solution rich in H ions, the H occlusion is carried out during the Pd deposition and growth period, which allows H diffusion from the surface layer.

ELECTRICAL AND ELECTRONIC ENGINEERING Thick Film Resistor Using Ruthenium Oxide

European Appl. 628,974A Thick film resistor composition comprises, by wt.%, 5-25 of divided solids of Ru oxide as a conducting component and 30-70 of glass as an inorganic binder, where the divided solids of Ru oxide have average specific surface areas of 2 30 m'lg and avera e crystallite size of 2 160 A, or 18-30 m21g and 220 1. The thick resistor is particularly used for vehicles, particularly in ignition equipment. The high voltage endurance characteristics obtained, were typified by ESD and controllable values of resistance and TCR.

Multilayer Magneto-Optic Recording Media EASTMAN KODAK CO. European Appl. 630,008A A magnetooptic recording medium structure includes a substrate, an amorphous seed layer and a recording multilayer deposited on it as alternating layers of Co and k, or Co and Pt-Pd. The seed layer thickness of < 20 nm is selected to improve the coercivity and square- ness of the Kerr hysteresis loop of the mdtilayer.

E. I. DU PONT DE NEMOURS & CO.

Platinum Metals Rev., 1995, 39, (2). 95

Metallisation for Hybrid Integrated Circuits A. T. & T. BELL LAB. US. Patent 5,356,526 Interconnections between conductive elements on the major surface of an insulating substrate comprise successive deposits: Ti, Pd-Ti, Cu, Ni and Au. The use of a T P d alloy avoids the occurrence of Pd residues remaining after the etching of the Ti layer.

Ruthenium Oxide Film for Integrated Circuits NORTHERN TELECOM LTD. US. Patent 5,358,889 A conductive layer of RuO, for an IC comprises an IC substrate with a layer of H,O soluble Rum) nitro- syl salt, a H,O soluble viscosity modifier, and a volatile organic acid, which is heated to 150-200°C to form an amorphous phase of Ru oxide. The amorphous Ru oxide layer is then annealed at 30G7OO"C to induce crystallisation to form a tetragonal RuO, phase which is suitable for formation on a perovskite structure fer- roelecmc material. The chloride-free process is com- patible with processing for submicron devices.

Integrated Circuit Package with Lead Frame AMERICAN TELEPHONE & TELEGRAPH CO.

U S . Patent 5,360,991 The composite includes the following successive layers: Ni, Pd or soft Au smke, Pd-Ni, Pd and Au. The Pd acts primarily as a bonding layer between the Ni and Pd-Ni alloy layers and as a layer that enhances reduction in porosity of subsequent layers. The Pd- Ni alloy layer acts as a trap for base metal ions. The Pd layer acts as a trap for Ni ions from the Pd-Ni alloy layer, and the outer Au layer enhances the quality to the Pd layer. This composite can withstand the effects of the processing steps in the fabrication of encap- sulated devices, while maintaining solderability.

Piezoelectric Ceramics for Resonator SUMITOMO METAL IND. LTD.

Japanese Appls. 61206,767-68 The ceramics comprise Pd-Sn niobate, Y-Pb titanate and Pb zirconate, or Pd, Sn, Nb, Pb, Ti, ZrO,, etc. The composition also includes 2.6-3.8 g atom Mn : 100 mol of the basic composition. The ceramics are used for a piezoelectric resonator or a filter and the composition prevents degradation.

Conductor Paste MURATA MFG. co. LTD. Yabanese Abbl. 6/260.016

Multilayer Interconnection Substrate HITACHI LTD. Japanese Appl. 61260,762 A method to manufacture multilayer interconnection substrate involves building on a ceramic substrate, coating with a Cr thin film, coating with a Cu thii film, followed by another Cr film. Resist is applied. The upper Cr film is etched, then Cu plated and the resist is removed, leaving an exposed Cu pattern. A Pd catalyser is applied to the Cu surface, followed by Ni plating, and a final polyimide film. This method gives detailed wiriig with a high aspect ratio. Wiring length is reduced by miniaturisation and the speed of operation is increased.

Magnetic Thin Film Material TEIJIN LTD. Japanese Appl. 61267,743 Magnetic thin film material for a magneto-optical recording medium includes a B8 type crystal structure having a unidirectional magnetic anisotropy and a Mn-Sb-Pt alloy. The alloy has a composition of formula Mn,SbJ't, (a = 40-60, b = 32-55, c = 1-20 and a+b+c = 100, by at.%), and a B8 type crystal structure in amount > 75 vol.%, is contained in the alloy. The film has good magnetic and optical properties.

Scratch Type Slide Brush TANAKA KlKINZOKU KOGYO K.K.

Japanese Appl. 6/27 5,3 5 6 A scratch type slide brush is provided with a bent L- shaped portion at one end which is coated with a layer of Rh. The end part may be made of precious metal. The life of scratch type slide brush is increased by greater wear resistance.

Manufacture of Semiconductor Devices MITSUBISHI ELECTRIC COW.

Japanese Appl. 61291,146 A manufacturing method for a semiconductor device, such as GaAs FET, involves formation of a gate electrode of Ti/Pt/Au on top of a WSi gate electrode on the fast elecmc conduction type layer with high impurity density. The current concentration of the drain electrode and the short channel effect are controlled. The build-up of bottlenecks is prevented by spread- ing the surface depletion layer.

MEDICAL USES _ _ Conductor paste is prepared by mixing metallic powders selected from Pd, Ag or Pd-Ag, with polymer binder, such as ethyl cellulose, and an additive. The

powder is beaded with an organic binder, of &,,I and solvent ofa-tapene oil. ~ ~ l - ~ t i ~ ~ is controlled by

N~~ ~~i~ platinum ~~~~l~~~~ World Appl. 94127,595A N. FARRELL

Tris (Pt) complexes contain neutral and/or anionic ligands, a di- or uiamine bridging agent, a counter- ion optionally dependent on whether the 3 Pt co-ordination sDheres have a net charge, and a net charge

the resin less combustible.

Coating Structure of Wiring Electrode of the counter-ions such that the resultant tris(fi)

a Au film of 0.0025 pm applied on the Pd film. The coating is used for substrate wiring of lead frames and bump electrodes of semiconductor devices.

The New Patents abstracts have been prepared from material published by Denvent Publications Limited.


Conductor Paste

Conductor paste is prepared by mixing metallic powders selected from Pd, Ag or Pd-Ag, with polymer binder, such as ethyl cellulose, and an additive. The metallic powder is kneaded with an organic binder, of ethyl cellulose and solvent of a-terpene oil. Delamination is controlled by making the resin less combustible.

Coating Structure of Wiring Electrode EREKKU AZUMA K.K. Japanese Appl. 61260,577 The coating structure of a wiring electrode comprises a conductor sheet member, a Cu film deposited on the outer surface, a Ni film deposited on the Cu film, a Pd film _< 0.5 p thick applied on the Ni film and a Au film of 0.0025 pm applied on the Pd film. The coating is used for substrate wiring of lead frames and bump electrodes of semiconductor devices.

MURATA MFG. CO. LTD. Japanese Appl. 6/260,016

New Tris Platinum Complexes N. FARRELL World Appl. 94/27,5 95A Tris (Pt) complexes contain neutral and/or anionic ligands, a di- or uiamine bridging agent, a counter- ion optionally dependent on whether the 3 Pt co-ordination spheres have a net charge, and a net charge of the counter-ions such that the resultant tris(Pt) complex is neutral, etc. The complexes are pharma- ceutical agents, for example for treating cancer, etc., and is administered orally or parenterally. Tris(Pt) complexes have enhanced DNA adduct formation compared to mono- or bis Pt complexes.

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