Transition-metal dithiolene complexes. Part XIX. Mixed 1,1-/1,2-dithiolene complexes of cobalt and iron

Abstract

The syntheses and characterisation of a series of mixed 1,1-/1,2-dithiolene complexes, [M(S2CNR2){S2C2(CN)2}2]2–(M = Co or Fe; R = Me or Et), [Fe(S2CNEt2)2{S2C2(CN)2}]– and [M(S2C:X){S2C2(CN)2}2]2–{M = Co or Fe; X = C(CN)2, C(CN)CO·OEt, C(CN)CO·NH2, CH·NO2, or N(CN)}, are described. A voltammetric examination of the complexes in dichloromethane established that the trianionic species, and [M(S2CNR2){S2C2(CN)2}2]2–, could be oxidised in a one-electron step, the half-wave potentials of which showed a small but significant dependence on R or X; the E½-values were also dependent on M. The dithiocarbamate adducts and [M{S2C:C(CN)2}{S2C2(CN)2}2]2– could be further oxidised. The bis-dithiocarbamate, [Fe(S2CNEt2)2{S2C2(CN)2}]–, could be irreversibly reduced to the corresponding dianion. Oxidation of the cobalt complexes was achieved chemically using iodine, and [Co(S2CNR2){S2C2(CN)2}2]– and [Co(S2C:X){S2C2(CN)2}2]2– were characterised by e.s.r. and electronic spectral studies; salts of [Co{S2C:CH·NO2}{S2C2(CN)2}2]2– and [Co{S2C:C(CN)CO·OEt}{S2C2(CN)2}2]2– were isolated. The dianionic species [Fe{S2C:C(CN)2}{S2C2(CN)2}2]2– was obtained by aerial oxidation of the corresponding trianion. The magnetic properties of the complexes are described briefly.