Electron-transfer reactions in non-aqueous media. II. Reduction of CoF(NH₃)₅²⁺, CoCl(NH₃)₅²⁺ and CoBr(NH₃)₅²⁺ by iron(II) in dimethyl sulphoxide-water mixtures

Abstract

The kinetics of the reduction of the cobalt(111) octahedral complexes, CoF(NH₃)₅²⁺, CoCl(NH₃)₅²⁺ and CoBr(NH₃)₅²⁺, by iron((11) in various Me₂SO-H₂O mixtures have been studied over a range of temperatures. The activation parameters obtained for the chloro and bromo systems are consistent with a change in the stereochemistry of the iron (11) atom in the bridged intermediate from octahedral in water to tetrahedral with increasing Me₂SO concentration. The fluoro system, however, has activation parameters which are less sensitive to solvent composition and consistent with the iron(11) atom maintaining octahedral coordination.