Abstract
The kinetics of oxidation of [Co^sup II^NM(H^sub 2^O)]^sup 3-^ (N = nitrilotriacetate, M = malonate) by N-bromosuccinimide (NBS) in aqueous solution have been found to obey the equation: d[Co^sup III^]/dt = k^sub 1^ K^sub 2^[NBS][Co^sup II^]^sub T^/{1 + K^sub 2^[NBS] + (H^sup +^/K^sub 1^)} where k^sub 1^ is the rate constant for the electron transfer process, K^sub 1^ the equilibrium constant for dissociation of [Co^sup II^NM(H^sub 2^O)]^sup 3-^ to [Co^sup II^NM(OH)]^sup 4-^ + H^sup +^, and K^sub 2^ the pre-equilibrium formation constant. Values of k^sub 1^ = 1.07 × 10^sup -3^ s^sup -1^, K^sub 1^ = 4.74 × 10^sup -8^ mol dm^sup -3^ and K^sub 2^ = 472 dm^sup 3^ mol^sup -1^ have been obtained at 30 °C and I = 0.2 mol dm^sup -3^. The thermodynamic activation parameters have been calculated. The experimental rate law is consistent with a mechanism in which the deprotonated [Co^sup II^NM(OH)]^sup 4-^ is considered to be the most reactive species compared to its conjugate acid. It is assumed that electron transfer takes place via an inner-sphere mechanism.[PUBLICATION ABSTRACT]