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(μ-Cl)2] (1) and [Ni2CdL′2Cl(H2O)]ClO4·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) [NiIICdII]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 [NiIICdIINiII] 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⋯Cl or O–H⋯Cl and O–H⋯O hydrogen bonding interactions are operative in the complexes to build up 2D supramolecular structures in their solid states.

Two heteropolynuclear complexes, [Ni2Cd2L2Cl2(μ-Cl)2] (1) and [Ni2CdL′2Cl(H2O)]ClO4·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 prepared and characterized by structural and other physicochemical studies. The complexes comprise heterotetranuclear [NiIICdII]2 or heterotrinuclear [NiIICdIINiII] units involving bridging chlorine and/or oxygen functions. H-bonding interactions are operative in building up their supramolecular structures.Figure optionsDownload as PowerPoint slideHighlights
► Heteropolynuclear Schiff base complexes of Cd(II) and Ni(II) have been prepared.
► The complexes possess chloro and phenoxo bridges together or the latter only.
► Interesting structural variations are observed in the complexes.
► Intermolecular H-bonding interactions are operative in the complexes.