ELECTRON-TRANSFER AT AN ENCAPSULATED COBALT(III) CENTER - KINETICS OFOXIDATION OF THIOUREA AND 1,1,3,3-TETRAMETHYL-2-THIOUREA IN AQUEOUS ACIDIC MEDIA

The stoichiometries, kinetics and mechanisms of oxidation of (NH2)2CS (I) and (Me2N)2CS (2) to the corresponding disulphides by Co(III)M (M = W12O408-) in aqueous HClO4 were investigated. The reaction with (1) follows the empirical rate law -d[oxidant] = k[reductant] [oxidant] wh ere k = 12.5 +/- 0.3 m-1 s-1 at 25-degrees-C, while that with (2) foll ows the equation -d[oxidant] = {a + b[reductant]}[reductant][oxidant] where a = 5.4 x 10(4) M-1 s-1 and b = 3.3 x 10(6) M-2 S-1 at 25-degree s-C. Free radicals are important in the reactions and possible reactio n mechanisms are suggested and discussed.