Kinetics and mechanism of oxidation of chromium(III)-guanosine complex by periodate

The oxidation kinetics of the chromium(III)-guanosine complex, [Cr-III(G)(H2O)(4)](3+) (G = guanosine) with periodate in aqueous solution were studied and found to obey the rate law: Rate = [Cr-III](T)[IO4-] (k(1)K(5) + (k(2)K(1)K(6) /[H+])} / {1 + (K-1/[H+]) + K-5[IO4-] + (K1K6[IO4-]/ [H+])} where K-1, K-5 and K-6 are the deprotonation of [Cr-III(G)(H2O)(4)](3+) and pre-equilibrium formation constants [Cr-III(G)(H2O)(3)-IOI3](2+) and[Cr-III(G)(H2O)(2)(OH)OIO3](+) precursor complexes respectively. 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).