Kinetic studies on the bromate ion oxidation of 12-tungstocobaltate(II) in aqueous acid

The oxidation of Co^IIW by bromine(V) is a complex process involving an induction period. The reaction was found to be first-order in both Co^IIW] and Br^v], and exhibits a complex dependence on H⁺]. These observations were successfully explained by considering HBrO₂, one of the intermediates formed in the direct but slow reaction between Co^IIW and bromine(V), as the reacting species. The first-order limiting dependence in H⁺] was due to the involvement of a protic equilibrium of HBrO₂. The induction period appears due to the scavenging effect of Br^– inadvertently present in the medium. It appears to be the first report where HBrO₂ was found to be the reacting intermediate in the oxidation of metal ions and complexes by BrO^– ₃.