Synthesis and crystal structure of two new heteropolynuclear [NiIICdIICdIINiII] and [NiIICdIINiII] Schiff base complexes involving bridging chlorine and oxygen functions

Two new heteropolynuclear Schiff base complexes, [Ni2Cd2L2Cl2(mu-Cl)(2)] (1) and [Ni2CdL2'Cl(H2O)]ClO4 center dot H2O (2) where L = [N,N'-bis(2-hydroxyacetophenylidene)]propane-1,2-diamine and L' = [N,N'-bis(2-hydroxypropiophenylidene)]propane-1,2-diamine, have been synthesized by refluxing equimolar amounts of nickel perchlorate, cadmium chloride and the respective tetradentate Schiff base ligand, H2L or H2L' in methanol medium. The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies on 1 reveal the presence of a bis(heterodinuclear) [(NiCdII)-Cd-II](2) unit in which the two central cadmium ions are doubly chloro-bridged with each other and each of them is connected to a nickel(II) center through two phenolate oxygen bridges. In contrast, complex 2 contains a heterotrinuclear [(NiCdNiII)-Cd-II-Ni-II] unit in which the central cadmium ion is connected to two nickel(II) centers through two doubly bridging phenolate oxygen atoms. The Cd(II) ions in 1 and 2 adopt distorted, square pyramidal (CdO2Cl3) and octahedral (CdO5Cl) geometries respectively. On the other hand, the Ni(II) ions in both 1 and 2 assume the same coordination geometry, i.e. a distorted square planar (NiO2N2) arrangement. Intermolecular C-H center dot center dot center dot Cl or O-H center dot center dot center dot Cl and O-H center dot center dot center dot O hydrogen bonding interactions are operative in the complexes to build up 2D supramolecular structures in their solid states. (C) 2011 Elsevier Ltd. All rights reserved.