The Bromination in Aqueous-Solution of Imidazole Coordinated to Co(NH₃)₅(³⁺)

Abstract

Bromination of imidazole coordinated to (NH₃)₅Co³⁺ (abbreviated Co) has been studied in aqueous Br^- media, I = 0.1, 0.5 mol dm^-3, 25.0°C; Co(4,5- Br₂ImH)³⁺ and Co(2,4,5-Br₃ImH)³⁺ result from treatment with Br²(aq). Co(4-BrImH )³⁺ has also been prepared and characterized. Rate data correspond to reaction of the conjugate base of the imidazole complex, Co(Br_xIm)²⁺ (x = 0, 1, 2), with Br₂, with successive bimolecular rate constants 6×10⁹, 3×10⁸ and 3.5×10³ mol^-1 dm³ s^-1. Possible mechanisms are discussed.