Abstract
The oxidation of [Cr-III(HIDA)(Asp)(H2O)(2)](+) by periodate in aqueous solution to Cr-VI have been found to obey the following equation.
rate = k(1) K-2 [Cr-III](T) [I-VII](T) {1 + [H+] / K-1 + K-2 [I-VII](T)}
where k(1) is the rate constant for the electron transfer process. K-1 the equilibrium constant for dissociation of [Cr-III(HIDA)(Asp)(H2O)(2)](+) to [Cr-III(IDA)(Asp)(H2O)(2)] + H+, K-2 the pre-equilibium formation constant. Values of k(1) = 3.38 x 10(-3) s(-1). K-1 = 1.74 x 10(-3) mod dm(-3) and K-2 = 8.3 mol(-1) dm(3) have been obtained at 45 degrees C and 1 = 0.2 mod dm(-3). Thermodynamic activation parameters have been calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4- to chromitlm(III).