Electron-transfer reactions in non-aqueous media. III. Reduction of CoF(NH₃)₅²⁺, CoCl(NH₃)₅²⁺ and CoBr(NH₃)₅²⁺ by iron(II) in N,N-dimethylformamide

Abstract

The reduction of the cobalt(111) octahedral complexes CoF(NH3)₅²⁺, CoCl(NH₃)₅²⁺ and CoBr(NH₃)₅²⁺ by iron(11) in HCONMe₂ proceeds through a mechanism involving reversible formation of a halide bridged binuclear intermediate prior to electron transfer and decomposition of the intermediate to products. Values of the activation parameters for reduction and the equilibrium constants for formation of the bridged intermediate are consistent with a tetrahedral stereochemistry for the iron(11) atom in the bridged intermediate for the chloro and bromo systems. However, for the fluoro system these values are consistent with the iron(11) atom maintaining octahedral coordination. These results are compared to those obtained in Me₂S0.^1,2