Kinetics and mechanism of oxidation in the diaqua(nitrilotriacetato)cobaltate(II)/N-bromosuccinimide reaction: evidence for iron(II) catalysis

Oxidation of the diaqua(nitrilotriacetato)cobaltate(II) complex, [Co(II)nta(H2O)(2)](-), by NBS has been studied in aqueous medium. The kinetics of the reaction in the presence of an iron(II) catalyst obey the rate law: d[Co-III]/dt = [Co(II)nta(H2O)(2)(-)]{[Fe2+](k(8) + k(9)K(1)/[H+]) + [NBS](k(12)k(10)/k(-10)k(12)) + K(1)k(11)k(13)/(k(-11) + k(13))[H+]} Catalysis by iron(II) is believed to be due to the oxidation of iron(II) to iron(III), which acts as the oxidizing agent. The thermodynamic activation parameters were calculated and we propose that electron transfer proceeds through an inner-sphere mechanism.