Transition-metal dithiolene complexes. Part XXI. Iron, cobalt, and nickel complexes containing chelating diarsine, diphosphine, and related ligands

Abstract

The complexes [M(L)(S–S)₂]^–[M = Fe or Co; (S–S)= S₂C₂(CN)₂, S₂C₂(CF₃)₂, or S₂C₆Cl₄; L =o-C₆H₄(AsMe₂)₂, Ph₂AsCH₂CH₂AsMe₂, cis-Ph₂PCH:CHPPh₂, Me₂PhP, or Me₂PhAs], [M(L)(S–S)₂]⁰[M = Fe or Co; (S–S)= S₂C₂Ph₂; L = Ph₂AsCH₂CH₂AsPh₂ or Me₂PhAs], [Fe(Ph₂As·CH₂·CH₂·AsPh₂){S₂C₂(p-MeC₆H₄)₂}₂]⁰, [Ni{o-C₆H₄(AsMe₂)₂}{S₂C₂)CN)₂}₂]⁰, and [M{o-C₆H₄(AsMe₂)₂}₂{S₂C₂(CN)₂}]⁰(M = Fe or Co), have been prepared. It has been shown spectrally and by voltammetry that the species [M(L))S–S)₂]^–, where L =o-C₆H₄(AsMe₂)₂, Ph₂AsCH₂·CH₂·AsPh₂ and cis-Ph₂P·CH:CH·PPh₂, are six-co-ordinate, whereas the species [M(L))S–S)₂]⁰, where L = Ph₂As·CH₂·CH₂·AsPh₂, are five-co-ordinate. The effect, on E½-values of the various couples studied, of conjugation within the chelating Lewis base ligand framework is discussed, and a Lewis base donor atom influence on half-wave potentials has been observed. The voltammetric behaviour of [M{o-C₆H₄(AsMe₂)₂}₂{S₂C₂(CN)₂}]⁰ was unexceptional.