) Indian Joual of Cהmistry Vol. 38A, September 1999, pp.961 -965 Synthesis and characterization of dioxouranium(VI) complexes of polydentate ligands S 1 Swamy* & K Bhaskar Department of Chemistry, University College Kakatiya University, Warangal 506 009, India Received II February 1998; revi sed 20 April 1 999 The polydentate ligands, N,N ' -ethylene-bis-(2 - aminobenzamide) [EBABl. N,N ' -propylene-bis -(2-amino- benzamide) [PBAB], N ,N ' -(o -phenylene) -bis-(2-amino- benzamide) r rhBABl. N , N ' -ethylene-bis -(3 -carboxy - propenamide) [EBCPl. N,N' -propylene-bis-(3-carboxy- propenamide) [PBCP] and 1 -(2'-hydroxyphenyl)- 3-phenyl- I ,3-propane-dione [HPPPD] react with uranyl acetate to form crystalline complexes with d if ferent coordination environ- ments. The geometries of the complexes have been confirmed with the help of the spectroscopic methods, conductance mea- surements and themlal studies. The neutral tetradentate ligands (EBAB, PBAB and PhBAB) form eight coordinate hexagonal bipyramidal complexes, while anion ic tetradentate ligands (EBCP and PBep) and tridentate ligand (HPPPD) form seven coordinate pentagonal bipyramidal complexes. Of late, a great interest has been developed on theoreti- cal as we l l as experimental chemistry of met al oxocations. Dioxour anium(VI) or UO/+ is one of the stable oxocations I and the complexes of UO,2+ have been studied extensively 2 . " because of the theore - tical interest in the linear O=U=O group, different structures6, detec- tion of uranium compounds in sea water and its impor- tance in relation to energy problems. In view of the emerging interest in extraction of uranium from differ- ent sources and importance of the coordination chemis- try of U0 2 2 + and in continuation of our earlier work7.X, we have synthesized complexes of dioxouranium with multidentat e ligands, N,N ' -ethylene-bis -(2- aminobenzamide) [EBAB], N ,N' -propylene -bis -(2 - aminobenzamide) [PBAB], N, N ' -(o-phenylene)-bis -(2- aminobenzamide) [PhBAB], N,N ' -ethylene -bis -(3 - carboxypropenamide) [EBCPl. N,N' -propylene-bis -(3 - carboxypropenamide) [PBCP] and 1-(2' -hydroxyphenyl- 3-phenyl - l ,3-propane-dione [HPPPD]. In this note we report the characterization of these complexes [1 - 6] using spectroscopic and physicochemical studies. Experimental Uranyl acetate and isatoic anhydride were procured from BDH and all other chemicals and so lvents used were of AR grade. The ligands were prepared by the methods reported earlier9• 11• Conductivity measurements of the complexes were made using a Digisun digital conductivity meter Model DI-909. Electronic spectra were recorded using Schimadzu 160A spectrophotometer. IR spectra were recorded in KBr pellets on a Perkin-Elmer 283-model spectrometer. IH NMR spectra in DMSO-d 6 were re- corded on Bruker 80 instrument and the CHN-analyses were performed using Perkin-Elmer-CHN analyzer 2400 at Institut f ur Anorganische und Analytische Chemie der Technischen Universitat Berlin, Germany. The percent- age of uranium was determined as oxin ate complex by the colorimetric method using the procedure described in literature l 2 . Preparation of complexes The ligand (2.36 mmo!) was dissolved in 30 ml of methanol. In case of EBAB, a suspension was used as it is insoluble in methanol. The solution of ligands with dissociable protons (EBCPH2, PBCPH 2 and HPPPD) was neutralized by adding methanolic solution of NaOHI CH,COONa. To this solution, 2.36 mmol of uranyl ac- etate, dissolved in 25 ml of methanol, was added and the contents were r e fluxed for 4 - 7 h. The complexes that separated, were filtered and washed with methanol. The solid products were suspended in 40 ml of methanol, heated while stirring continuously to remove unreacted reagents and filtered again. They were dried in vacuo over fused CaCI 2 ; the yield = 75 - 86%. Results and discussion Al l the complexes of dioxouranium(VI) prepared in the present investigation were found to be stable and non-hygroscopic. The results of elemental analyses and
Transcript
).
Indian Journal of Chemistry
Vol. 38A, September 1999, pp.961 -965
Synthesis and characterization of dioxouranium(VI) complexes
of polydentate ligands
S 1 Swamy* & K Bhaskar Department of Chemistry, University College Kakatiya University, Warangal 506 009, India
Received II February 1 998; revised 20 April 1 999
The po lydentate l i gands , N,N ' -e thy lene-bi s- (2-aminobenzamide) [EBABl. N,N' -propylene-bis-(2-aminobenzamide) [PB A B ] , N ,N' -(o-phenylene)-bis-(2-aminobenzamide) rrh B AB l . N , N ' -ethy lene-b i s - (3 -carboxypropenamide) [EB CPl. N,N' -propylene-bis-(3-carboxypropenamide) [PBCP] and 1 -(2'-hydroxyphenyl)- 3-phenylI , 3-propane-dione [HPPPD] react with uranyl acetate to form crystal line complexes with d ifferent coordination environments. The geometries of the complexes have been confirmed with the help of the spectroscopic methods, conductance measurements and themlal studies. The neutral tetradentate ligands (EBAB, PBAB and PhBAB) form eight coordinate hexagonal bipyramidal complexes, while anionic tetradentate ligands (EBCP and PBep) and tridentate l igand (HPPPD) form seven coordinate pentagonal bipyramidal complexes.
Of late, a great interest has been developed on theoretical as wel l as exper imenta l chemi stry of metal oxocations. Dioxouranium(VI) or UO/+ is one of the stable oxocations I and the complexes of UO,2+ have been studied extensively2." because of the theore
-tical interest
in the l inear O=U=O group, different structures6, detection of uranium compounds in sea water and its importance in relation to energy problems. In view of the emerging interest in extraction of uranium from different sources and importance of the coordination chemistry of U022+ and in continuation of our earlier work7.X, we have synthesized complexes of dioxouranium with mu l t identate l i gands , N ,N ' -ethy lene-bis- (2-aminobenzamide) [EBAB] , N ,N' -propy lene-bis - (2-aminobenzamide) [PBAB] , N,N' -(o-phenylene)-bis-(2-aminobenzamide) [PhBAB] , N,N ' -ethy lene-bis-(3-carboxypropenamide) [EBCPl . N,N' -propylene-bis-(3-carboxypropenamide) [PBCP] and 1 -(2' -hydroxyphenyl-
3-phenyl- l ,3-propane-dione [HPPPD] . In this note we report the characterization of these complexes [1 - 6] using spectroscopic and physicochemical studies.
Experimental
Uranyl acetate and isatoic anhydride were procured from BDH and all other chemicals and solvents used were of AR grade. The ligands were prepared by the methods reported earlier9• 1 1 •
Conductivity measurements of the complexes were made using a Digisun digital conductivity meter Model DI-909 . E lectron ic spectra were recorded us ing Schimadzu 1 60A spectrophotometer. IR spectra were recorded in KBr pellets on a Perkin-Elmer 283-model spectrometer. IH NMR spectra in DMSO-d6 were recorded on Bruker 80 instrument and the CHN-analyses were performed using Perkin-Elmer-CHN analyzer 2400 at Institut fur Anorganische und Analytische Chemie der Technischen Universitat Berlin, Germany. The percentage of uranium was determined as oxinate complex by the colorimetric method using the procedure described in l iterature l2 .
Preparation of complexes The l igand (2.36 mmo!) was dissolved in 30 ml of
methanol . In case of EBAB, a suspension was used as it is insoluble in methanol . The solution of l igands with dissociable protons (EBCPH2, PBCPH2 and HPPPD) was neutralized by adding methanolic solution of NaOHI CH,COONa. To this solution, 2.36 mmol of uranyl acetate, dissolved in 25 ml of methanol, was added and the contents were refluxed for 4 - 7 h. The complexes that separated, were filtered and washed with methanol. The solid products were suspended in 40 ml of methanol, heated while stirring continuously to remove unreacted reagents and filtered again. They were dried in vacuo over fused CaCI2 ; the yield = 75 - 86%.
Results and discussion
All the complexes of dioxouranium(VI) prepared in the present investigation were found to be stable and non-hygroscopic. The results of elemental analyses and
962 INDIAN J CHEM. SEC. A. SEPTEMBER 1 999
Table I - Physical and analytical data of dioxouranium(VI) complexes
SI No Complex Decomp. Temp."C
[U02(EBAB)(OAc)2] 232
2 [U02(PBAB)(OAc)2] 230
3 [UO/PhBAB)(OAc)2] 235
4 [UO/EBCP)(HP)] 254
5 [UO/PBCP)(HP)] 260
6 [U02(HPPPD)(HP)2] 265
other physical properties are given in Table I . Irrespective of the proportions of the uranyl acetate and the ligand used, the metal ion to ligand ratio in the products was found to be 1 : 1 and the analytical data confirm the same stoichiometry for the complexes. The molar conductances of the complexes, measured in DMSO at a concentration of 1 0·' M at room temperature were found to be very low ( 1 0 - 1 6 Ohml cm2 mol· I ), indicating them to be non-ionic 13· 14 . This nature of complexes necessitates the coordination of two acetate ions in the case of complexes 1, 2 and 3, containing neutral tetradentate l igands. The thermal and the IR spectral data confirm the same (vide infra). The non-ionic nature of the complexes 4, 5 and 6 confirms that the l i gands are deprotonated to give dianion before coordination and thus neutral ize the dipositive charge of the uranyl ion9.
The DSC and thermograms of all the complexes were recorded between room temperature and 500"C in air. The absence of endothermic peak: and any mass loss confirms that the complexes do not melt in the studied range of temperature but only decompose. The complexes 1, 2 and 3 show neither endothermic peaks in the DSC nor any mass loss in the TG up to 1 50" confirming the absence of either lattice held or coordinated water molecules. The first stage of decomposition between 230 and 350" (43.4, 44.6 and 47.0% respectively) indicates loss of ligand moieties leaving U02(CHFOO)2 and
Found (Calcd) %
C H N U
34.46 2.96 7.87 35.03
(34.98 3.05 8. 1 6 34.69)
35.67 3.62 7.9 1 34. 3 1
(36.00 3.7 1 8.00 34.00)
38.79 3.42 7.44 3 1 .82
(39.23 3 .27 7.63 32.43)
23.63 1 .94 4.89 46. 1 5
(23.53 2.35 5.49 46.66)
24.58 2.39 4.86 44.76
(25 . 1 8 2.39 5.34 45.42)
32.76 2.47 44. 1 3
(33 .09 2.57 43.75)
finally the loss of acetate ions leaving metal oxide as residue. The amount of residue left was found to be slightly less than that required for UPK' confirming the contaminat\on with some U02 (ref I 5) . The complexes 4 and 5 show an endothermic peak between 1 30 and 1 50", with mass loss corresponding to one coordinated water molecule l6 The resulting anhydrous complexes decomposed losing the organic moiety and leaving a residue, with a percentage slightly more than that calculated for U,Ox. This could be ascribed to the presence of some carbon along with U30X. The complex 6, shows two endothermic peaks in the range of 1 1 0- 1 45" in DSC curves indicating the presence of two water molecules in the coordination sphere l6, and the final residue left after the loss of ligand was found to be 32.8% which is slightly more than that calculated for Upx (32. 1 7%) 17 .
In the IR spectra, the carbonyl stretching band of ligand EBAB ( 1 625 cm· l) shifts to higher frequency side in the spectra of the respective complexes ( 1 635- 1 660 cml) indicating non-coordination of the C=O grouplX. The three v(N-H) bands of the ligands at 3460, 3360, 3275 cml [EBAB and PBAB] and 3450, 3360 and 3290 cm· 1 [PhBAB] shifted to low frequency side by 30-90 cml indicating the coordination of amine (-NH) and amide (-CONH) groupSl9. In the spectra of the complexes, two bands are observed in the region between 1 570 and 1 520 cm·l , the one at lower frequency side may be as-
, �
-'.
..(.
...
....
�
NOTES 963
Table 2 - I H NMR spectral data of ligands and their uranyl complexes
4.8 (2H) 6.6 ( I H) 7.4 - 8.05 on (9H) 1 1 .20 ( I H) 1 6.50 ( I H)
Complex
1
2
3
4
5
6
cribed to the amide-II [v(C-N) + v(N-H)] and the other to the asymmetric stretch of the coordinated acetate group20. This is further confirmed by the presence of another absorption band around 1 360 cm- ! assignable to v(COO) . These two absorptions confirm the presence sym of the acetate group in the coordination sphere (low con-ductance values) and the formation of uranyl acetate after the first stage decomposition in the thermal analysis .
0, ppm Assignment
4.3 - 4.7 Aliphatic H's
3.82 -NH2 8.60 -CO-NH
7.3 - 7.8 Aromatic H's 2.4 - 2.5 (6H) CHJ of acetate ion
3.35 -N-CH2 1 .55 -C-CH2-C-
3.78 -NHz 8.8 -CO-NH-
2.6 (6H) CHJ of acetate ion
3.65 -NH2 8.77 -CO-NH
7.3 - 7.8 Aromatic H's
2.45 - 2.65 (6H) CHJ of acetate ion 4.3 - 4.7 Aliphatic H's
In the IR spectra of complexes of EBCP and PBCP, the amide N-H band is shifted to a lower frequency, while the amide carbonyl band to a h igher frequency, indicating the coordination of amide n itrogen atom_ The characteristic absorption of -COOH group observed in the IR spectra of l igands at 1 700 cm- ! disappears in the spectra of complexes and two new bands, one at 1 550 cm! and the other at 1 370 cm- ! assignable to [V(COO-)asym] and [V(COO-)sym] respectively appear confi rming the
964 INDIAN J CHEM, SEC. A, SEPTEMBER 1 999
deprotonation and coordination of carboxylic group. Further, the presence of a broad band between 3570 and 3300 cml and a sharp absorption at 850 cml confirms the coordination of a water molecule to the UO/+ ion.
The IR spectrum of complex 6, exhibits characteristic absorptions of coordinated �-diketone group, i. e. , at 1 600 cml [V(C=O)] and 1 5 I O cml [V(C=C)].2 1 The broad absorption band between 3500 and 3200 cm· 1 and a sharp one at 840 cml indicate the presence of coordinated water molecules. The v(C-O) of phenolic group in the ligand ( 1 285 cm- I ) lowered to 1 240 cm-I confirming its coordination. All the complexes exhibit v(M-N) and v(M-O) absorptions around 450-420 cm- I and 320 cml respectively. The absorption between 860 and 890 cm-I is characteristic of v(O=U=O) group22. 23 .
The IH NMR spectra of the complexes of dioxouranium(VI) and the l igands have been recorded in DMSO-do and the data (0, ppm) are given in Table 2 . The signals due to -NH2 and -CO-NH protons show a downfield shift which indicates coordination through amine -NH2 and amide -NH groups. The appearance of a signal in the high field side (methyl H's) confirms the presence of acetate group in the coordination sphere. The coordination of water molecules is evidenced from the signal at 3 .6 ppm in the spectra of complexes 4, 5 and 6.
. The disappearance of the signal corresponding to carboxylic acid protons of EBCP and PBCP in the spectra of the respecti ve complexes , 4 and 5, ind icates deprotonation. The absence of the signals at 1 6.50 and 1 I .20 ppm in the spectra of the complex, 6, confirms the loss of enolic and phenolic protons of the ligand HPPPD, and its coordination through the oxygen atoms.
The electronic spectra of U022+ are often complex. In
the two types of equatorial non-centrosymmetric complexes, DSH and D3H, the crystal field describes on one side, the axial field of the two oxygen atoms containing the l inear entity, O=U=O, and on the other side the equatorial field of the other l igands. The coordinating atoms of the ligands usually situated in a plane perpendicular to the uranyl ion axis, cause strong perturbations. The uranyl ion possesses two highest occupied orbitals 1tu and cr and the lowest unoccupied (non-bonding) orbit-u als cI> and cr +. A series of excited state of configura-" " tions are generated from the ground state configuration [(1tY, (crY](refs 24, 25). The complexes, 1 · 6, exhibit five to eight absorptions in the electronic spectra of the complexes in the range of 375-540 nm.
The analysis of the data of the complexes confirms that, in the case of complexes 1 . 3, six l igand atoms are
Structure · I
coordinated in addition to the two oxygen atoms ofUO/+, while in complexes 4 • 6, five ligands are coordinated. The results indicate the geometry of the complexes to be hexagonal bipyramidal ( 1 • 3) and to be pentagonal bipyramidal (4 · 6). The tentative structures of the complexes are shown in Structure I.
Acknowledgement
One of the authors (B. K) thanks the UGC, New Delhi for the award of a Junior Research Fellowship.
References Greenwood N N & Ernshaw A, Chemistry of the elements (Pergamon Press, Oxford) ( 1 986) p 1 467.
• 2 Tabushi I, Kobuke Y, Ando K, Kishimoto M & Oharo E, J Am
chem Soc, 1 02 ( 1 980) 5947.
3 Shinkai S, Subak T, Sone T & Manabe 0, Tetrahedron Lett, 26 ( 1 985) 3343.
6 Wells A F, Structural inorganic chemistry, (Oxford University Press, London) 4th Edn, ( 1 975) p 988.
7 Venkatanarayan G, Swamy, S J & Lingaiah P, Indian J Chem, 24A ( 1985) 624.
NOTES 965
8 Mrudula Rao B V, Swamy S J & Lingaiah P, Illdian } Chem, 1 7 Duval C, lnorgallic thermogravimetric analysis, (Elsevier Pub-24A ( 1 985) 887. lishing Company, New York) ( 1 963) p 659.
9 Bala Swamy G, Ravinder V & Swamy S J, /lldiall } Chem, 32A 1 8 Swamy S J , Kumar, B K & Dharmapuri Y, lndian } Chem, 34A ( 1 993) 589. ( 1 995) 8 1 1 and references therein.
1 9 Sandhu S S , Manhas B S , Mittal M R & Parmar S S , Indian } 1 0 Swamy S J & Kumar B K , Indiall } Chem, 35A ( 1 996) 489. Chem, 7 '( 1 969) 286. I I Gilman H & Blatt A H, Orgallic synthesis, (John Wiley & Sons, 20 Nakamoto K, Infrared spectra of inorganic and coordination
Inc, London) ( 1 950) p 205. compounds, (Wiley-Interscience, New York) ( 1970) p 1 52. 1 2 Vogel A I , A text book of quantitative inorganic analysis, (ELBS 2 1 Vigato P A , Casellato U, Tamburni S, Vidali M , Milani F &
& Longman, London) ( 1 975) p 899. Musiani M M , /llorg chim Acta, 6 1 ( 1 982) 89.
1 3 Gearwy W J, Coord Chem Rev, 7 ( 1 97 1 ) 8 1 . 22 Cattalin C, Crato U, Degetto S & Tandello E, lnorg chim Acta,
5 ( 1 97 1 ) 1 9. 1 4 Patil M S, Deora H 0 , Kulkarni M M & Shah J R, } Indian 23 Hisch A T T, Sheahan R M & West B 0, Aust } Chem, 28
chem Soc, 60 ( 1983) 8 1 7. ( 1 975) 885. 1 5 Duval C, Anal chim Acta, 20 ( 1 983) 266. 24 Denning R G, Snellgrove T R & Woodwork D R, Mol Phys, 30 1 6 Venakatanarayana G , Swamy S J & Lingaiah P, } Indian chelll ( 1 979) 1 1 09 and references therein.
![[j-38a-c-2012] in the supreme court of pennsylvania western district ...](https://static.documents.pub/doc/80x56/586b6b0d1a28abdf0a8bc7bd/j-38a-c-2012-in-the-supreme-court-of-pennsylvania-western-district-.jpg)