MONOTHIOCARBOXYLATE COMPLEXES OF OSMIUM(III) WITH FLUORO-THIOLATES AND DIMETHYLPHENYLPHOSPHINE CO-LIGANDS - X-RAY CRYSTAL-STRUCTURES OF [OS(SR)(2)(SOCCH3)(PME(2)PH)(2)] (R=C6F5 OR C6F4H-4)

Treatment of the pentacoordinated complexes [Os(SR)(3)(PMe(2)Ph)(2)] ( R = C6F5 or C6F4H-4) with R'COSH (R' = CH3 or C6H5) in acetone gave th e blue paramagnetic osmium(III) derivatives [Os(SC6F5)(2)(SOCR')(PMe(2 )Ph)(2)] (1) and [Os(SC6F4H-4)(2) (SOCR')(PMe(2)Ph)(2)] (2). Mass spec trometric data are given. X-ray crystallography has shown that 1 (R' = CH3) and 2 (R' = CH3) have an octahedral structure with trans-thiolat es, cis-phosphines and a chelating monothioacetate ligand. The electro chemical reduction of these compounds was studied by cyclic voltammetr y in DMF. The potential at which the compounds undergo reduction was f ound to be nearly independent of the nature of the substituent group o n the monothiocarboxylate ligand and slightly more dependent on the id entity of the substituent group on the thiolate ligands, the reduction becoming easier for the more electron-withdrawing thiolate derivative s.