Aquation of penta-ammine(dimethyl sulphoxide)cobalt(III) perchlorate in non-aqueous solvent–water–perchlorate media
Abstract
The aquation rate constant for penta-ammine(dimethyl sulphoxide)cobalt(III) perchlorate has been determined in 71 different solvent media and at three different temperatures for each medium. The average enthalpy and entropy of activation, their standard deviations, and ranges are 24.6 ± 0.4 and 23.6–25.6 kcal mol–1 and 1.1 ± 1.2 and –2.4 to 4.4 cal K–1 mol–1, respectively, without noticeable trends. The aquation rate constant is independent of ionic strength at constant perchlorate-ion concentration, but shows a specific perchlorate-ion effect. These results are discussed in terms of the Id and Bennetto–Caldin mechanisms. It is concluded that there is, at most, only a very small solvent contribution to the activation parameters.