Synthesis, Electronic and ESR Spectral Studies on Five-Coordinate Copper(II) Chloride Complexes with Monoacyl-Hydrazines and Hydrazones

Abstract

Copper(II) complexes of the type [CuLm (H2O)n] Cl2 and [Cu L′(H2O)2Cl]Cl, where L = benzoylhydrazine or isopropanone benzoylhydrazone and L′ = isonicotinoylhydrazine or isopropanone isonicotinoylhydrazone, m = 1 or 2 and n = 1 or 3 were prepared and characterized using elemental analyses, molar conductance, electronic, ESR and infrared spectral studies. The electronic and ESR spectra indicate a five-coordinate square- pyramidal geometry in the solid state and six-coordinate tetragonally-distorted octahedral geometry in DMSO for all the complexes. Solution studies show interaction of the solvent (DMSO) molecules with copper(II) in the axial plane. ESR data reveal rhombic symmetry for most of the complexes in the solid state except for the isopropanone benzoyl hydrazone complex which is isotropic in nature. However, the DMSO solution spectra give invariably axial signals for all the complexes at 300 K and 77 K. The trend g∥ > g⊥ > ge observed in all the complexes suggests the presence of an unpaired electron in the dx2−y2 orbital of copper(II). Bonding parameters α2, α2 and β1 2 have also been calculated from the ESR data. The hydrazide ligands bond to copper(II) through >C˭O and −NH2 groups, whereas the hydrazones bond through >C˭O and >C˭N groups. Referee I: W. E. Rudzinski Referee II: S. O. Sommerer