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

SUBHASIS MALLICK, BIPLAB K BERA, SUBALA MONDAL, PARNAJYOTI KARMAKAR, ARUP MANDAL and ALAK K GHOSH*

Department of Chemistry, The University of Burdwan, Burdwan 713104, India

*Corresponding author. E-mail: alakghosh2002@yahoo.co.in

MS received 21 April 2010; revised 21 December 2010; accepted 17 January 2011

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 liganddependent, 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.

Graphical Abstract. 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 involving formation of the ring-opened intermediate followed by ring closure is proposed.

Keywords. Kinetics; palladium(II); diethyldithiocarbamate; mechanism; activation parameters.