Mixed Ligand Chelates of Thorium(IV)

Abstract

29p. Mixed ligand chelates of thorium(IV) were prepared in solution and studied potentiometrically. These new compounds were formed by the reaction of various bidentate ligands with Th(IV) chelates of multidentate ligands such as ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid, N- hydroxyethylethylenediaminetriacetic acid, and nitrilotriacetic acid. When the stoichiometry ratios of the two ligands are such that the coordination vacancies of the metal ion are completely filled, the mixed ligand chelates thus formed are usually more stable toward hydrolysis than the analogous Th(IV) chelates containing only one type of ligand. The results obtained with a wide variety of mixed chelates of Th(IV) indicate that they may be divided into several classifications, depending on the order in which the ligands coordinate with the metal, on whether or not hydrolysis steps take place, and on whether the system disproportionates into a mixture of complexes each containing one type of ligand. (auth)