INNER-SPHERE OXIDATION OF ETHYLENEDIAMINETETRAACETATOCOBALTATE(II) BY N-BROMOSUCCINIMIDE

The kinetics of oxidation of [Co-II(EDTA)](2-) (EDTA=ethylenediaminetetraacetate) by N-bromosuccinimide (NBS) in aqueous solution obey the equation: Rate=k(2)K(3)[Co-II](T)[NBS]/{1+[H+])/K-2+K-3[NBS]} where k(2) is the rate constant for the electron-transfer process, K-2 the equilibrium constant for the dissociation of [Co-II(EDTAH)(H2O)](-) to [Co-II(EDTA)(OH)](3-) and K-3 the pre-equilibrium formation constant. The activation parameters are reported. It is proposed that electron transfer proceeds via an inner-sphere mechanism with the formation of an intermediate which slowly generates hexadentate [Co-III(EDTA)](-).