Cobalt(II), copper(II), zinc(II) and palladium(II) Schiff base complexes: Synthesis, characterization and catalytic performance in selective oxidation of sulfides using hydrogen peroxide under solvent-free conditions

摘要

An asymmetric bidentate Schiff-base ligand (HL: 2-tert-butyliminomethyl-phenol) was prepared from the reaction of salicylaldehyde and tert-butylamine. Cobalt(II), copper(II), zinc(II) and Pd(II) complexes, CoL2, CuL2, ZnL2 and PdL2, were synthesized from the reaction of CoCl2 center dot 6H(2)O, CuCl2 center dot 2H(2)O, Zn(NO3)(2)center dot 6H(2)O and PdCl2 with the bidentate Schiff base ligand HL in methanol. The ligand and its metal complexes were characterized by elemental analysis (CHN), FT-IR and UV-Vis spectroscopy. In addition, H-1 and C-13 NMR techniques were employed for characterization of the ligand (HL) and the diamagnetic complexes (ZnL2 and PdL2). The molecular structures of all the complexes were determined by the single crystal X-ray diffraction technique. The crystallographic data reveal that in all the complexes the metal centers are four-coordinated by two phenolate oxygen and two imine nitrogen atoms of two Schiff base ligands. The geometry around the metal center in the CoL2, CuL2 and ZnL2 complexes is a distorted tetrahedral and for PdL2 it is square-planar.