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. Δ S# of activation correlates well with the extrema in physical properties of the mixtures which are related to changes in solvent structure. Linear plots of Δ H# versus Δ S# were obtained and the isokinetic temperature indicates that the reaction is entropy controlled.