Synthesis, characterisation, and X-ray crystal structure of new Ni ^II, Pd^II, and Pt^II complexes of tridentate pyrazole-based ligands with an NOS-donor set

Treatment of the ligands 1-(3-thia-5-hydroxypentyl)-3,5-dimethylpyrazole (thpd) and 1-(3-thia-6-hydroxyhexyl)-3,5-dimethylpyrazole (thhd) with [PdCl 2(CH3CN)2], [PtCl2(CH 3CN)2], and NiCl2·6H2O produces the complexes [MCl2(L)] [M= Pd, L = thpd (1), thhd (2); M = Pt, L = thpd (3), thhd (4); M = Ni, L = thpd (5), thhd (6)], which have been characterised by elemental analyses, conductivity, IR, electronic spectra, and NMR spectroscopy (when possible). The crystal structures of 2, 3, and 4, determined by single-crystal X-ray diffraction, each consist of discrete [MCl2(L)] units, Each MII atom is coordinated by the pyrazolyl nitrogen and the thioether sulfur from the ligand and two cis chloride ions in a square-planar geometry. Crystallisation of [NiCl 2(thpd)] in non-anhydrous alcohols yields [NiCl(H2O) 2(thpd)]Cl ([7]Cl), the crystal structure of which was determined by single-crystal X-ray diffraction to reveal nickel atoms coordinated by two water molecules, one chloride ion and one thpd ligand (coordinating via all three donor atoms, N, S, and O) in a skew-trapezoidal bypyramid (distorted octahedral) geometry. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.