Aquation of penta-ammine(dimethyl sulphoxide)cobalt(III) perchlorate in water–non-aqueous solvent mixtures

Abstract

The aquation rate constant of penta-ammine(dimethyl sulphoxide) cobalt(III) ion in various aqueous and aqueous–non-aqueous solvent mixtures has been determined. The rate constant does not correlate well with water activity, the Grunwald–Winstein solvating-power Y parameter, or the heat of mixing of dimethyl sulphoxide with the solvent components. The data support an I_d mechanism more readily than a D mechanism. The activation enthalpy and entropy are 23·9 ± 0·7 kcal mol^–1 and 0·36 ± 2·29 cal K^–1 mol^–1, respectively.