Syntheses, crystal structures and spectroelectrochemical studies of two isomeric binuclear osmium carbonyl compounds [{Os(CO)(2)Ph}(2) {mu-eta(2)-C(NNPh)(2)}(2)]

Treatment of (diphenylthiocarbazono)phenylmercury [PhHg{SC(NNPh)(2)}] with the triosmium cluster [Os-3(CO)(10)(NCMe)(2)] produced two structural isome rs 1a and 1b of formulae [{Os(CO)(2)Ph}(2){mu-eta(2)-SC(NNPh)(2)}(2)] in 35 and 20% yield, respectively. The complexes were fully characterised by IR, H-1-NMR, mass spectroscopies and X-ray crystallography. The isomers 1a and 1b show no significant metal-metal interaction and are different in the ar rangement of the organic ligand. Complex 1a was found to undergo a complete conversion to 1b in the presence of excess reducing agent Co(Cp)(2). The e lectrochemical and spectroelectrochemical (UV-vis) properties of these two complexes are described. (C) 1999 Elsevier Science S.A. All rights reserved .