Kinetics of the solvolysis of trans-chloroazidobis(1,2-diaminoethane)cobalt(III) ions in water and in water + propan-2-ol mixtures

Abstract

Although previous kinetic results on the solvolysis of trans-[Coen₂N₃Cl]⁺ in water + co-solvent mixtures suggest that plots of log (rate constant) against the reciprocal of the dielectric constant are linear and independent of the co-solvent used, such a plot for propan-2-ol as co-solvent shows considerable curvature. The conclusion that might be drawn from the earlier results that the influence of solvent structure on the initial and transition states is about the same does not apply here and the application of a free-energy cycle to the process initial state → transition state in water and in the mixed solvent shows that the effect of solvent structure dominates the complex in the transition state. Enthalpies and entropies of activation for the solvolysis are correlated with changes in the physical properties of the mixtures and are compared with those for the cis-complex.