The crystal structures and properties of copper (II) and zinc (II) complexes of ß-diketones and aromatic N-oxides

Abstract

This work describes a study of the structures and properties of copper(II) and zinc(II) complexes. Copper and zinc chloride complexes of pyridine N-oxide and its methyl derivatives were prepared and characterized. Elemental analysis, molecular weights, unit cell dimensions, space groups, densities, and thermal properties were determined for the complexes. Copper and zinc complexes of trifluoroacetylacetone, hexafluoroacetylacetone, and trifluorobenzoylacetone were also prepared and studied. Most of the beta-diketone complexes were isolated as hydrates, and one form of bis(trifluoroacetylacetonato) zinc(II) exists as a trimer. The complexes having a 1:1 ratio of N-oxide ligand per copper chloride have anomalously low magnetic moments. The X-ray crystal structure of the pyridine N-oxide complex of ClCl2 ,was determined, and it was found to be dimeric. Magnetic interactions between the copper ions take place through the bridging oxygens of the pyridine N-oxide units. The structure of Cu3Cl6(2-picoline N-oxide)2 dot 2H20 was found to consist of copper ions bridged by oxygen atoms and chloride ions to form polymeric chains. The chains appear to be linked to each other by hydrogen bonding between water molecules and chloride ions. The complexes having a 2:1 ratio of N-oxide to copper(II) chloride often occur in both yellow and green forms. Most are monomeric. The green form of (4-picoline N-oxide)2CuCl2 is trans square planar. The crystal structure of the yellow form of (2,6- lutidine N-oxide)2CuCl2 has a configuration intermediate between tetrahedral and cis square planar. The N-oxides form only 2:1 monomeric complexes with zinc chloride. A tetrahedral structure was found for the (2,6-lutidine N-oxide)2ZnCl2 complex. -