Kinetics of solvent exchange and ligand substitution reactions of metal ions in relation to structural properties of the solvent

Activation parameters of solvent exchange and ligand substitution reactions of metal ions are discussed in relation to structural properties. Solvent exchange is treated as a particular case of ligand substitution. A general relation between enthalpy and entropy of activation is shown to hold for both types of reaction at divalent metal ions for a wide variety of solvents and ligands, after corrections have been made for ligand-field stabilisation. Water occupies a middle position in the range of solvents. The results are interpreted in terms of a structural model for a solvated ion in solution, based on that of Frank and Wen.