Electron transfer reactions in non-aqueous media. Part I. Reduction of CoF(NH 3) 52+, CoCl(NH 3) 52+ and CoBr(NH 3) 52+ by iron(II) in dimethylsulphoxide

Abstract

The kinetics of the reduction of the cobalt(III) octahedral complexes CoF(NH 3) 5 2+, CoCl(NH 3) 5 2+ and CoBr(NH 3) 5 2+, by iron(II) in dimethylsulphoxide (DMSO) have been studied over a range of temperatures, ionic strengths and acidities. As in water the results are consistent with an inner-sphere atom transfer mechanism. An extraordinary change in activation parameters, compared with the aqueous chemistry, for the chloro and bromo systems in DMSO, is interpreted in terms of a change in the stereochemistry of the iron(II) atom in the bridged intermediate.