Kinetics and mechanism of oxidation of the chromium(III)-DL-aspartic acid complex periodate reaction. Evidence for iron(II) catalysis

The kinetics of oxidation of the chromium(III)-DL-aspartic acid complex, [( CrHL)-H-III](+) by periodate have been investigated in aqueous medium. In t he presence of Fe-II as a catalyst, the following rate law is obeyed: d[Cr-VI]/dt = [(CrHL+)-H-III]{[Fe-II] (k(7) + K(1)k(8)/[H+]) + [I-VII] ((k(9)k(11)/k(-9) + k(11)) + (K(1)k(10)k(12)/(k(-10) + k(12)) [H+]))} Catalysis is believed to be due to the oxidation of iron(II) to iron(III), which acts as the oxidizing agent. Thermodynamic activation parameters were calculated. It is proposed that electron transfer proceeds through an inne r-sphere mechanism via coordination of IO4- to Cr-III.