Anion and solvent effects on the coordination behavior of N-(2-pyridinylmethylene)benzoylhydrazone with copper(II): Synthesis and structural characterization

The Cu(II) complexes [Cu(HL)Cl₂], 1; [Cu(HL)(NO₃)(H₂O)]NO₃, 2a; [Cu(L)(NO₃)]₂·C₃H₈O, 2b; [Cu(L)(μ_1,1-N₃)]₂, 3; [Cu(L)(Br)]₂, 4; [(H₂O)CuL(-SO₄)CuL], 5a; [CuL(-SO₄)CuL]·H₂O, 5b and [Cu(L)(CH₃COO)]₂, 6, where HL is a benzoylhydrazone tridentate Schiff base, have been synthesized and characterized by elemental analysis, FTIR, and UV-vis. The structures of 2a, 2b, 3, 4, 5a, and 5b have been determined by single-crystal X-ray diffraction analyses. In 2a, the benzoylhydrazone ligand is neutral and coordinates in its keto form and copper(II) has a distorted octahedral geometry. In dinuclear 2b, 3, 4, 5a, and 5b, there are bridging counter anions and the benzoylhydrazone ligand is monoanionic, coordinating in its enol form. In 5a and 5b, the enolic ligand also supplies a bridging alkoxo to the adjacent copper ion. In 5a, one of the two copper ions is five-coordinate in a distorted square pyramidal geometry, while the other copper ion has an additional water bonded to it in a distorted octahedral geometry. In 5b, both copper ions are five-coordinate with distorted square pyramidal geometries.