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(μ-SO₄)CuL], 5a; [CuL(μ-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.