Exchange in mixtures of cadmium with bis(benzimidazoles)

Abstract

Mixtures of cadmium salts and benzimidazoles have been examined by ¹H, ¹³C and ¹¹³Cd NMR spectroscopy in dimethyl sulfoxide and in dimethyl sulfoxide–chloroform mixtures. Evidence of exchange processes both for cadmium entities and for ligand entities was obtained. Structure–shift relationships for ¹¹³Cd NMR signals were examined, but were found not to apply. The exchange was slowed in the mixed solvent and on cooling, permitting individual components to be identified (the cadmium entities with stoichiometry CdL₃, CdL₂, CdL, and solvated Cd, identified from the cadmium NMR spectra, and ligand-containing species CdL₂ from proton spectra). Structural hypotheses relating to complexes are made and the role of these species in the observable exchange processes is explored.