Spectroscopic, thermal and X-ray crystal structure studies of some bis-(pyrazine-2-carboxylato) nickel(II) complexes

Abstract

Three nickel(II) complexes [Ni(PC)2(H2O) 2], 1, [Ni(PC)2(TU)2], 2 and [Ni(PC) 2(ABI)2]·2(H2O), 3, PC = pyrazine-2-carboxylate, TU = thiourea and ABI = 2-aminobenzimidazole, were synthesized and characterized by elemental analysis, IR spectroscopy and thermal analysis. The complexes were also investigated by single crystal X-ray diffraction analysis. Structures of the monomeric complexes showed nickel(II) chelated to two PC ions from an oxygen atom of carboxylate ion and the adjacent hetero nitrogen atom. The three complexes were crystallized in a monoclinic system with P21/c space group for 1, while 2 and 3 had C2/c space groups. The structure of 1 showed two coordinated water molecules occupying the trans positions of a slightly elongated octahedron. The structure of 2 consisted of two PC ions and two thiourea molecules in trans positions. The structure of 3 was different and showed a highly distorted octahedron with two ABI molecules chelated to the nickel ion in cis positions through their hetero nitrogen atoms. Two water molecules of crystallisation were shown in the structure of 3. © 2005 Taylor & Francis.