Octahedral cobalt(III) complexes of the chloropentammine type. XVII. Association and reaction of some halogenopentamminecobalt(III) and halogenopentamminechromium(III) cations with hydroxide in aqueous dioxan

Abstract

The replacement, by hydroxide ion, of the coordinated halide from some halogenopentamminecobalt(III) and ‐Chromium(III) cations in aqueous dioxan has been studied over a range of alkali concentrations up to 0.1 M. With excess of hydroxide ion at constant ionic strength, pseudo first‐order rate constants were obtained. The results support a pre‐equilibrium association of complex and hydroxide ions in these media, but do not provide distinction as to whether the resulting ion‐pair subsequently reacts by direct exchange or by proton removal. The extents of ion association are found to be greater for the cobalt(III) than for the chromium(III) system, increasing with the amount of dioxin in the solvent mixture.