Kinetics of the oxidation of bromide ions by tris(2,2′-bipyridine)nickel(III) ions in aqueous perchlorate media: comparison with oxidation by aqua-cations

Abstract

The rate of oxidation of bromide ions by [Ni(bipy)₃]³⁺ is first order in [Ni(bipy)₃³⁺] and first order in [Br^–]. The second-order rate constant is independent of acidity in the range 1–5 mol dm^–3 HClO₄ at a constant ionic strength of 5.00 mol dm^–3, and the slow step is a simple interaction of [Ni(bipy)₃]³⁺ with Br^– without removal of any co-ordinated 2,2′-bipyridrne from the Ni atom before the electron transfer. Intermediate complexes between the reactants are not detected. This is contrasted with the oxidation of Br^– by aqua-cations and is compared with the oxidation of H₂O₂ by [Ni(bipy)₃]³⁺.