Reduction of tetranuclear µ-oxalato-cobalt(III) complexes by the ions chromium(II) and vanadium(II)

Abstract

The kinetics of reduction of three highly charged tetranuclear µ-oxalato-cobalt(III) complexes by the ions Cr²⁺ and V²⁺ have been studied. All four cobalt(III) centres of each complex are reduced and the first stage of reaction is rate determining. Second-order rate constants k_Crand k_v for the chromium(II) and vanadium (II) reactions have been obtained and the ratios k_Cr : k_v at 25 °C are 0·022, 0·017, and 0·020. It is concluded that the mechanism of reduction is in each case outer sphere. Activation parameters have been determined for the Cr²⁺ reduction of two of the complexes, and the magnitude of these parameters is discussed.