Effect of solvent on the reactions of coordination complexes. Part 22.1. Kinetics of base hydrolysis of some(aminomonocarboxylato (tetraethylenepentamine)cobalt(III)complexes in acetonitrile-water media:the role of solvent basicity and solvent structure

Abstract

The base of hydrolysis of [(tetren)CoO2CR]²⁺ {R=NH2CH2-, NH2[CH2]2-, pyridine-2- (αβS isomer), NH2CH(CH3)- (αβS and αβR isomers); tetren=tetraethylenepentamine} is accelerated by acetonitrile+water media (0=XAN=0.578, XAN=mole fraction of acetonitrile) owing to the combined effects of destabilisation of OH^-, relatively greater destabilisation of the transition state of the amido conjugate base [((tetren)-H)Co^2+-O2 CR]^+* as compared to that of the initial state [(tetren)CoO2CR]²⁺, and solvent structure; the activation enthalpies and entropies are also sensitive to solvent structure and conformational arrangement of the tetren ligand.