Ligand exchange reactions between copper(II)- and nickel(II)-chelates of different sulfur- and selenium-containing ligands

Abstract

Rapid ligand exchange reactions between copper(II)-chelates of different sulfur- and selenium-containing ligands could be detected in chloroform and acetone respectively by means of EPR. Most of the combinations belong to one of the following classes: • —mutual combinations of dichalcogenocarbamates yield the mixed ligand chelates in the ratio 1:1:2 (starting chelates to product), expected for random organization; • —combinations of copper(II)-dichalcogenocarbamates with copper(II)-bis-maleonitriledithiolate yield the corresponding mixed ligand complexes exclusively. The second type can be used to prepare mixed maleonitriledithiolato-carbamato-complexes from solutions simply by mixing the components and adding an appropriate solvent. Several examples are given. In addition also reactions between copper(II)- and nickel(II)-chelates of the same ligands are included. The different behavior of the combinations is reflected by the differences of the total electron energies of reactants and products obtained by EHT-treatment of model compounds. Voltammetric half-wave potentials of the mixed ligand chelates depend on the alkyl groups of the carbamates, on the metal ion and on the S/Se ratio in the coordination sphere.