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.