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Osmium dithiophosphates. Synthesis, X-ray crystal structure, spectroscopic and electrochemical properties

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Title Osmium dithiophosphates. Synthesis, X-ray crystal structure, spectroscopic and electrochemical properties
 
Creator JAIN, PRATEEK U
PAUL, HIMADRI
MUNSHI, PRADIP
WALAWALKAR, MRINALINI G
LAHIRI, GOUTAM KUMAR
 
Subject electrospray
x-ray diffraction
spectroscopic analysis
 
Description The reactions of ammonium salt of dialkyldithiophosphate ligands, (RO)2PS2 −NH4 + (R=Me/Et) with (NH4)2OsIVBr6 in methanol solvent and under dinitrogen atmosphere result in one-electron paramagnetic tris complexes, {(RO)2PS2}3OsIII (1a–1b) in the solid state. The molecular structure of one complex (1a) has been determined by single-crystal X-ray diffraction. It shows the expected pseudo-octahedral geometry with reasonable strain due to the presence of four-membered chelate rings. The reflectance spectra of the solid complexes display two broad bands in the range 552–484 nm and in the solid-state complexes exhibit one isotropic EPR signal at 77 K. Although the complexes 1a–1b are found to be stable in the solid state, in solution state the complexes are transformed selectively into the diamagnetic and electrically non-conducting metal–metal bonded dimeric species [{(RO)2PS2}3OsIII–OsIII{S2P(OR)2}3]. The formation of dimeric species in the solution state is authenticated by the electrospray mass spectrum of one representative complex where R=Et (1b). In dichloromethane solution the complexes show two moderately strong sulfur to osmium charge-transfer transitions in the visible region and two strong ligand based transitions in the UV region. The complexes exhibit successive two oxidations correspond to OsIV–OsIV/OsIII–OsIII and OsV–OsV/OsIV–OsIV processes near 0.8 and 1.9 V versus SCE, respectively. One reductive couple corresponds to the OsIII–OsIII/OsII–OsII couple has been observed near −0.6 V. Electrochemically generated oxidized species [{(RO)2PS2}3OsIV–OsIV{S2P(OR)2}3]2+ display lowest energy ligand to metal charge-transfer transition near 550 nm which has observed to be reasonably red shifted as compared to that of the parent trivalent species. On the other hand electrochemically generated reduced species [{(RO)2PS2}3OsII–OsII{S2P(OR)2}3]2− are found to be unstable even on coulometric time scale.
 
Publisher Elsevier
 
Date 2009-04-03T09:04:34Z
2011-11-25T20:36:01Z
2011-12-26T13:08:14Z
2011-12-27T05:56:15Z
2009-04-03T09:04:34Z
2011-11-25T20:36:01Z
2011-12-26T13:08:14Z
2011-12-27T05:56:15Z
2001
 
Type Article
 
Identifier Polyhedron 20(3-4), 245-252
0277-5387
http://dx.doi.org/10.1016/S0277-5387(00)00638-0
http://hdl.handle.net/10054/1119
http://dspace.library.iitb.ac.in/xmlui/handle/10054/1119
 
Language en