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≤X_AN≤0.578, X_AN=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)Co²⁺≡^-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.

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