Syntheses and characterization of nickel(II), zinc(II) and palladium(II) complexes derived from three pyrazole-based polydentate ligands

Two pyrazole-based polydentate ligands, 1,3-bis(5-methyl-3-phenylpyrazol-1-yl)-propan-2-ol (Hmppzpo) and 1,3-bis(5-methyl-3-p-isopropylphenylpyrazol-1-yl)-propan-2-ol (Hmcpzpo), have been synthesized. A third ligand, 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-2-ol (Hdmpzpo), has been synthetically modified. Seven new M(II) coordination compounds of general formula M2L2X2 (M = Zn, Ni; X = NO3 or ClO4; L = dmpzpo, mppzpo or mcpzpo) or MLX (M = Pd; L = dmpzpo; X = Cl) were synthesized and structurally characterized by elemental analysis and FT-IR analysis. The crystal structures of [Zn-2(mu-dmpzpo-O,N,N')(2)(NO3)(2)] center dot 2H(2)O (1 center dot 2H(2)O), [Ni-2(mu-dmpzpo-O,N,N')(2)(CH3CN)(2)](ClO4)(2) (2) and Pd(mu-dmpzpo-N,N')Cl-2 (4) were determined by single-crystal X-ray crystallography. The crystal structures show that complexes 1 center dot 2H(2)O and 2 are center-symmetric dinuclear compounds, with two metal ions bridged by two alkoxo groups and each metal ion with a distorted square-pyramidal environment. The palladium complex, 4, displayed square-planar coordination geometry around the Pd(II) ion with trans arrangement.