Magnetic and spectroscopic studies on metal complexes of some oxygen-nitrogen and sulphur-nitrogen chelating agents

Abstract

Abstract New Schiff base ligands, formed by condensation of acetylacetone with N-methyl-S-alkyldithiocarbazates, and their nickel(II) chelates having the general formula, Ni(ONNSR)2 (R = CH3 and -CH2C6H5; ONNSR is the deprotonated form of a Schiff base) have been prepared and characterized by IR and electronic spectroscopic techniques. The complexes, Ni(ONNSR)2 are green but diamagnetic and contain the NiO2N2 chromophore instead of the expected NiO2N2S2 group. On the basis of magnetic and spectroscopic evidence square-planar structures are assigned to these complexes. The copper(II) complex, Cu(HONNSR)Br2 containing the neutral Schiff base ligand was also isolated. Magnetic and spectroscopic data support a square-planar structure for the Cu(HONNSR)Br2 complex. Hydrated copper(II) chloride or copper(II) perchlorate salts promote complete hydrolyses of the Schiff bases with the concomitant formation of copper(II) complexes of N-methyl-S-alkyldithiocarbazate ligands. Both mono- and bis-ligand complexes having the general formulas, Cu(NSR)X2 (R = CH3, CH2C6H5; X = Cl−, Br− and Cu(NSR)2(ClO4)2, respectively, were isolated and studied by magnetic and spectroscopic techniques. The mono-ligand complexes, Cu(NSR)X2 are thought to possess halogen-bridged polymeric structures. Variable-temperature magnetic susceptibility data for the above complexes fit the Curie-Weiss law with small θ values. The bis-ligand complexes, Cu(NSR)2(ClO4)2 contain coordinated perchlorate groups and are highly explosive in nature. Magnetic, conductance, and spectroscopic data are in accord with a distorted octahedral structure.