The electrochemical behaviour of organonickel complexes: Mono-, di- and trivalent nickel

The redox properties of organometallic nickel complexes of the type [(a-diimine)Ni(Mes)Br], [(a-diimine)Ni(MeS)(2)] and the complexes trans-[(PPh3)(2)Ni(Mes)Br] and trans-[(PPh3)2Ni(Fmes)Br] [Mes = mesityl (2,4,6-trimethylphenyl); Fines = tris(2,4,6-trifluoromethyl)phenyl] have been studied in detail by various electrochemical and spectroelectrochemical (UV/ Vis/NIR and EPR) methods. Upon electrochemical reduction, the bromido mesityl derivatives undergo cleavage of the mide ligand. The resulting reactive species and their products from follow-up reactions are investigated. Electrochemical oxidation leads to formally trivalent nickel species. The metal contribution to the unpaired electron for the formally monovalent and trivalent nickel species can be estimated from EPR spectroscopy. (c) Wiley-VCH Verlag GmbH & Co. KGaA.