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)center dot(2)2H(2)O

The coordination mode of the title ligand, HL4Me (synthesized and character ized by mass, IR and H-1 NMR spectral parameters) is reported by solid-stat e isolation and physicochemical identification of a few bis complexes of ni ckel(II) with different counterions. Magnetic and electronic spectral featu res classify the reported species, [Ni(HL4Me)(2)]X-2 . 2H(2)O, as six-coord inate, pseudo-octahedral with appreciable tetragonal distortion. Vibrationa l spectral data have indicated a neutral tridentate (NNS) function of HL4Me through the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and th iocarbonyl sulphur. X-ray crystallographic studies of [Ni(HL4Me)(2)](NO3)(2 ) . 2H(2)O (triclinic, P (1) over bar) has unambiguously proved the distort ed octahedral environment of the nickel(II) ion; the ligand molecules are t rans coordinated to the central nickel(II) ion. (C) 1998 Elsevier Science L td. All rights reserved.