SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF NICKEL(II) COMPLEXES WITH 3,5-DIMETHYL-1-(O-AMINOPHENYL)PYRAZOLE (DAPPZ) - X-RAY CRYSTALLOGRAPHIC STUDIES OF [NI(DAPPZ)2(H2O)2]CL2.H2O AND [NI(DAPPZ)2(NCS)2].H2O

The coordination mode of the title ligand, DApPz (synthesized and characterized by mass, IR and PMR spectral parameters), is reported by solid-state isolation and physico-chemical identification of a host of bis complexes of nickel(II) with different counter-ions. Magnetic and electronic spectral features classify the reported species, [Ni(DApPz)2X2]. nH2O, as six-coordinate, pseudo-octahedral with appreciable tetragonal distortion. Vibrational spectral data have indicated a neutral bidentate (N-N) function of DApPz through the pyrazolyl (tertiary) ring nitrogen and the aminophenyl nitrogen. In most cases, the counter-ion is coordinated to the nickel(II) ion, but in some cases the water molecules complete the octahedron. X-ray crystallographic studies of [Ni(DApPz)2(H2O)2]Cl2.H2O (monoclinic, P2(1)/n) and [Ni(DApPz)2(NCS)2].H2O (triclinic, P1BAR) have unambiguously proved the octahedral environment of the nickel(II) ion; the ligand molecules are cis coordinated to the central nickel(II) ion in both cases. A cis configuration of the coordinated water molecules and the counter-ions (NCS) is established on the basis of an O(W)-Ni-O(W) angle of 88.3-degrees and an N(NCS)-Ni-N(NCS) angle of 94-degrees.