Electrochemical studies of perfluoroalkyl and alkyl derivatives of cobalt(III) with quadridentate salicylaldimines at mercury and platinum electrodes

Abstract

The electrochemical reduction at mercury and platinum electrodes of a series of perfluoroalkyl (R_F) and alkyl (R_H) cobalt(III)NN′-ethylenebis(salicylaldimines)[CoR(salen)] has been studied in tetrahydrofuran by several techniques. Each class of compound is reduced similarly, [Co^IIIR(salen)] [graphic omitted] [Co^IIR(salen)]^– [graphic omitted] [Co^IR(salen)]^2–, with the Co^IIIR_F complexes reducing most readily. Electron transfer and subsequent chemical reaction rates are different at the mercury and platinum electrodes implying that mercury-bridged intermediates may be formed at the mercury electrode. The [CoR_F(salen)]^– species are more stable than the alkyl complexes but do decompose to [Co(salen)] and perfluorocarbanions. The [CoR_H(salen)]^– anions rapidly yield [Co(salen)]^– and the alkyl radical. Both complexes [CoR(salen)]^2– decompose very rapidly to [Co(salen)]^–.