Kinetics and mechanism of oxidation of chromium(III)-L-glutamic acid complex by periodate

The kinetics of oxidation of the chromium(III)-L-glutamic acid complex, [CrIII(L)(2)(H2O)(2)](+), by periodate in aqueous solutions has been found to obey the following equation: d [Cr-VI] / dt =k(2) K-5[Cr-III]T[I-VII](T) /(1+ ([H+] /K1) + K-5[I-VII](T)} where k(2) is the rate constant for the electron transfer process, KI the equilibrium constant for dissociation of [Cr-III(L)(2)(H2O)(2)(+)] to [CrIII(L)(2)(H2O)(OH)] + H+, and K-5 the pre-equilibrium formation constant. Values of k(2) = 2.93 x 10(-3) s(-1), K-I = 6.26 X 10(-4) mol dm(-3) and K-5 = 88.41 dm(3) mol(-1) have been obtained at 30 degreesC and I = 0.2 mol 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 chromium(III).