G. Pedrosa, J. A. Salas, M. Katz
Mar 1, 1983
Citations
0
Influential Citations
11
Citations
Journal
Journal of Coordination Chemistry
Abstract
Abstract The kinetics of piperidine replacement by pyridine at the pentacyano(piperidine) ferrate (II) complex has been investigated under pseudo-first-order condition in acetonitrile + water mixtures from a mole fraction of acetonitrile x 2=0 to x 2=0.122 at constant ionic strength (I=1 mol dm−3, NaCl). The rate constants at 25, 30 and 35° increase on addition of acetonitrile. Transition state solvation predominates over initial state solvation on account of more enhanced releasing ligand-bulk solvent interactions which occur when the mechanism is of a dissociative type. The greater hydrophobic nature of the transition state is indicated by a negative correlation between the difference in activation free energies (δ m δG#) and the excess free energy for the solvent mixture (G E ). Thus, when the aqueous mixture becomes richer in acetonitrile, the transition state is stabilized and the rate constant increases. The enthalpies and entropies of activation seem to show inflection points at x 2 ≅ 0.04, in corr...