Synthesis and characterization of a binuclear copper(II) complex [Cu(H₂slox)]₂ from polyfunctional disalicylaldehyde oxaloyldihydrazone and its heterobinuclear copper(II) and molybdenum(VI) complexes

Abstract

The binuclear copper complex [Cu(H₂slox)]₂ (1) and heterobinuclear copper and molybdenum complexes [Cu(slox)MoO₂(A)₂] (slox = tetranegative disalicylaldehyde oxaloyldihydrazone) (A = H₂O (2), py (3), 2-pic (4), 3-pic (5), 4-pic (6)) and [Cu(slox)MoO₂(NN)] (NN = bpy (7) and phen (8)) have been synthesized from disalicylaldehyde oxaloyldihydrazone in methanol and characterized by various physico-chemical and spectroscopic techniques. The stoichiometry of the complexes has been established based on elemental analyses and thermoanalytical studies. The µ _eff values for the complexes rule out metal–metal interaction between the metal centers in the structural unit of the complexes. The dihydrazone has keto-enol forms; in 1, it is a dibasic tetradentate bridging ligand in enol form and in heterobinuclear complexes as a tetrabasic hexadentate bridging ligand. Electronic spectra of the complexes show that copper(II) is square-planar in binuclear and heterobinuclear complexes; molybdenum is a distorted octahedral stereochemistry in heterobinuclear complexes. EPR spectra suggest that in all complexes, the unpaired electron is in the d _{x 2− y 2} orbital of copper and that the copper in heterobinuclear complexes is tetrahedrally distorted.

Keywords:

• Heterobinuclear complexes
• Copper(II)
• Dioxomolybdenum(VI)
• Disalicylaldehyde oxaloyldihydrazone
• Spectral studies