Kinetics of aquation of dichloro tetrapyridine ruthenium(II) complex in binary aqueous solvents

Abstract

First-order solvolysis rates of trans-dichloro tetrapyridine ruthenium(II) have been measured UV spectrophoto metrically over a wide range of solvent compositions in temperature ranges(40-55°C) in water-2-propanol and water-t-butanol mixtures. The rate of solvolysis is faster in the former than in the latter. Plots of log (rate constant) versus the reciprocal of relative permitivity of the co-solvent gave a non-linear relation for both co-solvents, this non-linearity is derived from a large differential effect of solvent structure between the initial and transition states. ΔS# of activation correlates well with the extrema in physical properties of the mixtures which are related to changes in solvent structure. Linear plots of ΔH# versus ΔS# were obtained and the isokinetic temperature indicates that the reaction is entropy controlled.