Abstract
The kinetics of the solvolysis of the hydrophobic ion, Co(4-t-Bupy)(4)Cl-2(+), have been followed in mixtures of water with co-solvents having a hydrophilic tendency, ethane-1,2-diol and 2-methoxyethanol. The variation of In(rate constant) with the reciprocal of the dielectric constant is nonlinear for both co-solvents. The enthalpy and the entropy of activation are rather insensitive to changes in the solvent composition in both mixtures, but low maxima may exist at mol fractions of co-solvent Ca. 0.10-0.20. The application of a Gibbs energy cycle to the process of the initial state going to the transition state suggest that, in water-rich conditions, the increase in the stability of the emergent solvated Co-III ion in the transition state relative to the increase in the stability of Co(4-t-Bupy)(4)Cl-2(+) in the initial state as the co-solvent content rises is greater for 2-methoxyethanol than for ethane-1,2-diol. (C) 1995 John Wiley & Sons, Inc.