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

Abstract 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 ](ClCH 2 COO) 2 , 2 and [Ni(iz) 6 ](CH 3 ClCHCOO) 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⋯O bonds, in which all the N–H imidazole units, as well as all the carboxylate O 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  · 2H 2 O ( 4 ) shows a two-dimensional hydrogen-bond network in which only four ligands take part along with Cl − and H 2 O units. The distortion of Ni 2+ 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.