Acid- and base-catalysed displacement of the carboxylate ligand from [Pt(dien)(RCO2)]+(dien = 1,5-diamino-3-azapentane; R = CH2Cl, CHCl2, or CCl3) in aqueous solution

Abstract

The kinetics of the displacement of the carboxylate ligand from [Pt(dien)(RCO₂)]⁺(dien = 1,5-diamino-3-azapentane; R = CHCl₂ or CCl₃) have been studied and are compared with the data for R = CH₂Cl. Although the intrinsic reactivity is very sensitive to the basicity of the leaving group, the nucleophilic discrimination is independent of the nature of the leaving group and is the same as that of [Pt(dien)Cl]⁺. The acid-catalysed pathway for solvolysis, which dominated the reaction of the chloroacetate complex, is far less important for the displacement of CHCl₂CO₂^– and not observed for CCl₃CO₂^–. The solvolysis is accelerated by added hydroxide, the rate law taking the form k_obs.=k₀+k₁[OH^–]+k₂[OH^–]². The relative contribution of the three pathways depends upon the basicity of the leaving group.