Complexes of Cu(II), Co(II) and Ni(II) with pyrazole-derived ligands. Crystal structure of {bis[3-phenyl-5-(2-pyridyl)pyrazolato, κN1:κN2]copper(II)}

The reaction of the pyrazole derived-ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL0) and 3-phenyl-5-(6-methyl-2-pyridyl)pyrazole (HL1) with Cu(CH3COO)2, Co(CH3COO)2 and Ni(CH3COO)2 was carried out. Products were characterised by elemental analyses, conductivity measurements and infrared and electronic spectroscopy. The IR spectra of complexes display the typical absorption bands of pyrazole-derived ligands. The nature of the complexes depends on the metal, M, the ligand, HL, and the M:HL ratio: Ni(HL)2(CH3COO)2, Cu(L)2, (HL=HL0, HL1), Co(L0)2. In the complexes of Co(II) and Cu(II) the pyrazole is deprotonated, the band ν(N–H) was not observed in IR spectroscopy. The crystal structure of [Cu(L0)2] consists of discrete centrosymmetric molecules involving a co-ordinated CuN(pz)2N(py)2 core with planar geometry. The anionic ligand L0 is not completely planar.