Hydrolysis of some trans-dichlorobis(diamine)cobalt(III) cations by base

Abstract

The kinetics of the replacement, by hydroxide ion, of the first co-ordinated chlorine in trans-[Co(AA)₂,Cl₂]⁺ cations have been studied and the Arrhenius parameters calculated, where AA represents a C- or N-alkyl substituted ethylenediamine ligand. It is shown that when AA is so changed that the steric congestion at the reaction site is progressively increased, the rate of replacement at first falls and then rises. This relation constitutes evidence for the duality of mechanism, which is also supported by activation energies. It is believed that the reaction does not take place by a conjugate base mechanism,¹ but through pre-equilibrium formation of ion-pairs.