Kinetics and mechanism of the oxidation of a ternary complex involving nitrilotriacetatocobaltate(II) and malonic acid by N-bromosuccinimide

Abstract

The kinetics of oxidation of [CoIINS(H2O)2]3− by N-bromosuccinimide (NBS) in aqueous solution has been studied spectrophotometrically in the 20–40 °C range. The reaction is first order each in [NBS] and [CoIINS(H2O)2]3−, and the rate of reaction increases with increasing pH between 6.64 and 7.73. The thermodynamic activation parameters have been calculated. The experimental rate law is consistent with a mechanism in which the deprotonated [CoIINS(H2O)(OH)]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.