Electron spin resonance studies of the ligand exchange in cupric complexes with diethyldithiocarbamate and diethyldithiophosphate as ligands

Abstract

The kinetics of ligand substitutions in the cupric complexes where a diethyldithiocarbamate (dtc) is replaced by a diethyldithiophosphate (dtp) has been studied with chloroform as solvent. The relative concentrations of the paramagnetic species produced in the reactions have been determined using electron spin resonance. The reaction studies suggest the presence of the short time equilibria: Cu (dtc) + dtpH ⇋ Cu (dtc) (dtp) + dtcH Cu (dtc) (dtp) + dtpH⇋Cu (dtp) + dtcH where the equilibrium constants have the value, 0.0625 and 0.00143 respectively. The equilibria are disturbed by the reaction: dtcH + dtpH → (C H)2 NH + dtp+ CS with a rate constantk = 0.07 1. mole sec. at 26°C. Analysis of the thermodynamic parameters determined from the study of the kinetics of the reactions at various temperatures shows that dtp group favours more solvent and excess ligand coordination than dtc. This is consistent with the study of "Long time equilibrium" which indicates that Cu (dtp) exists with further two weakly bonded dtpH groups in the axial positions in chloroform solutions.