Metal complexes derived from hydrazoneoxime ligands: IV. Molecular and supramolecular structures of some nickel(II) complexes derived from diacetylmonoxime S-benzyldithiocarbazonate

Four new nickel(II) complexes, [{Ni(L)}(2)], [NiL center dot HPyr], [NiL center dot HIm] and [Ni(HL)(2)]center dot H2O, derived from diacetylmonoxime-S-benzyldithiocarbazonate (H2L) have been synthesized and characterized by elemental analyses, field desorption and electrospray ionization mass spectra, UV-Vis, infrared absorption spectra, as well as H-1 NMR spectra. X-ray molecular structures showed that the Ni(II) in both [NiL center dot HPyr] and [NiL center dot HIm] are in a distorted square planar environment and is coordinated to the dianionic NNS tridentate hydrazoneoxime ligand via deprotonated oximate nitrogen, hydrazone imine nitrogen, and thiolate sulphur. The fourth coordination sites are occupied, respectively, by the pyrazole and imidazole nitrogens. The oximate O1 of [NiL center dot HPyr] is involved in intramolecular hydrogen bond with the pyrazole NH proton as well as intermolecular hydrogen bond pyrazole C6H proton, forming a helical chain propagating along the b-axis. The structure is stabilized by a set of pi center dot center dot center dot pi and CH center dot center dot center dot pi interactions. The molecular units in [NiL center dot HIm] are linked together by hydrogen bond formation between the oximate oxygen and imidazole NH proton, giving rise to an infinite zigzag chain extended along the a-axis. The chains are interconnected by pi center dot center dot center dot pi and CH center dot center dot center dot O interactions. In [Ni(HL)(2)]center dot H2O, the Ni(II) is in a distorted octahedral environment. The two mononegative hydrazoneoxime ligands are coordinated in the meridional configuration where the two thiol sulphur atoms and the two oxime nitrogen atoms are cis to each other, while the imine nitrogen atoms are trans. The oxime proton O2H is involved in a reciprocal bifurcated hydrogen bond formation with both N2 and S3 of the adjacent molecule giving rise to hydrogen bonded dinner. This dimeric structure is further stabilized by a pair of reciprocal CH center dot center dot center dot O interactions. A one dimensional chain of alternating dimeric unit and water molecule propagating along the c-axis is formed via hydrogen bond formation between the oxime O1 oxygen and the bridged water molecule proton. (C) 2008 Elsevier Ltd. All rights reserved.