Synthesis and spectroscopic characterization of nickel(II) complexes with 5-methyl-3-formylpyrazole-N(4)methylthiosemicarbazone (HL4Me):: X-ray crystallographic studies of [Ni(HL4Me)2](NO3)•22H2O

The coordination mode of the title ligand, HL4Me (synthesized and characterized by mass, IR and H-1 NMR spectral parameters) is reported by solid-state isolation and physicochemical identification of a few bis complexes of nickel(II) with different counterions. Magnetic and electronic spectral features classify the reported species, [Ni(HL4Me)(2)]X-2 . 2H(2)O, as six-coordinate, pseudo-octahedral with appreciable tetragonal distortion. Vibrational spectral data have indicated a neutral tridentate (NNS) function of HL4Me through the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiocarbonyl sulphur. X-ray crystallographic studies of [Ni(HL4Me)(2)](NO3)(2) . 2H(2)O (triclinic, P (1) over bar) has unambiguously proved the distorted octahedral environment of the nickel(II) ion; the ligand molecules are trans coordinated to the central nickel(II) ion. (C) 1998 Elsevier Science Ltd. All rights reserved.