Structural characterization and magnetic properties of hexakis(imidazole)nickel(II) bis(formate), bis(chloroacetate), bis(2-chloropropionate) and hexakis(1-methyl-imidazole)nickel(II) chloride dihydrate

The nickel(II) complexes of formula [Ni(iz)(6)]X-2, (where iz = imidazole, and X = formate, chloroacetate and 2-chloropropionate anions) have been prepared and characterized by spectroscopic methods and magnetic measurements. The crystal and molecular structure of [Ni(iz)(6)](HCOO)(2), 1, [Ni(iz)(6)](ClCH2COO)(2), 2 and [Ni(iz)(6)](CH3ClCHCOO)(2), 3 have been determined by X-ray diffractions methods. The structure of the all complexes is formed by a three-dimensional network consisting of [Ni(iz)(6)](2+) cations interlinked by formate, chloroacetate and 2-chloropropionate anions through three different N-H center dot center dot center dot O bonds, in which all the N-H imidazole units, as well as all the carboxylate 0 atoms, take part. The Ni atom is in a nearly octahedral environment formed by the tertiary nitrogen atom of the imidazole moieties. An analogous complex [Ni(Meiz)(6)]Cl-2 center dot 2H(2)O (4) shows a two-dimensional hydrogen-bond network in which only four ligands take part along with Cl- and H2O units. The distortion of Ni2+ coordination polyhedron rises in the order of 1(negative) <2 <3(positive) <4. The magnetism of complexes exhibits a zero-field splitting D. the magnitude of which correlates with the distortion degree of the coordination polyhedra. (C) 2005 Elsevier Ltd. All rights reserved.