Mono- and bis-chelated nickel(II) complexes of the di-2-pyridylketone Schiff base of S-methyldithiocarbazate and the X-ray crystal structure of the bis[S-methyl-beta-N-(di-2-pyridyl)-methylenedithiocarbazato]nickel(II) complex

The di-2-pyridylketone Schiff base of S-methyldithiocarbazate (Hdpksme) rea cts with nickel(II) salts giving both mono- and bis-chelated complexes of e mpirical formulae, [Ni(dpksme)X] (dpksme = anioninc form of the Schiff base . X = NCS-, Cl-) and [Ni(dpksme)(2)], respectively. These compounds have be en characterized by magnetic and spectroscopic techniques. The mono-ligated nickel(II) complexes are four-coordinate and square-planar but the bis-lig and complex is six-coordinate and octahedral. The crystal and molecular str ucture of [Ni(dpksme)(2)] has been determined by X-ray crystallography. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the py ridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfu r atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The ligand and its nickel(II) complexes exhibit weak antimicrobial activity against the pathogenic bacteria, S. dysenteriae, B. cercus, S. aureus and E. coli and the fungi, A. alternata and M. phaseolina. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.