Kinetics and mechanism of the ligand substitution reaction of di-μ-hydroxobis(bipyridyl)dipalladium(II) ion with diethyldithiocarbamate anion in aqueous solution

Abstract

The kinetics of the interaction between diethyldithiocarbamate (Et2DTC) and the title complex has been studied spectrophotometrically in aqueous medium as a function of nucleophile concentration, temperature and pH at constant ionic strength. The reaction is a two-step process in which the first step is ligand-dependent, but the second step is ligand-independent and is assigned to ring closure. The rate and activation parameters, conductivity studies and IR data were used to deduce a plausible mechanism. The kinetics of the interaction of diethyldithiocarbamate with di-μ-hydroxobis-(bipyridyl)dipalladium(II) ion in physiological pH at a constant ionic strength was studied spectrophotometrically. The reaction in aqueous medium exhibits a 2:1 metal ligand ratio. A two-step consecutive mechanism \(\left( {\text{A}\xrightarrow{{\text{k}_\text{1} }}\text{B}\xrightarrow{{\text{k}_\text{2} }}\text{C}} \right)\) involving formation of the ring-opened intermediate followed by ring closure is proposed.