Binuclear copper(I) complexes derived from xylyl binucleating ligands and their carbonyl and imidazole adducts

Abstract

The binuclear copper(1) complexes of the ligands, N,N~’,N’-tetrakis[2-(4-Z-benzylidenimino)ethyl]-~,~-diamin~~-xylene, MXBA (Z = H) and MXPNB (Z = NOz), have been obtained as diperchlorate salts. The complexes are unreactive toward dioxygen in the solid state and in solution provided that dry solvents are used. Binding by the donor groups of the ligands to the copper(1) centers has been investigated by IR and N M R spectroscopy. It has been concluded that in solution two imine and one tertiary amine nitrogen donors are coordinated to each metal ion, with additional binding by a solvent molecule. In the solid state the imine groups are coordinated, while binding by the tertiary amine groups cannot be established. These binuclear complexes form dicarbonyl and diimidazole adducts that are stable to oxidation but display somewhat weak binding of copper(1) to the added ligand. Electronic, and in the case of the diimidazole adducts, perhaps also steric effects account for this apparently low affinity of copper(1) for the added ligands.