Tetrakis(1-benzyl-1H-imidazole)dichloridonickel(II)

In the title compound, [NiCl2(C10H10N2)4], the NiII ion is located on an inversion center being coordinated by four N atoms from two pairs of symmetry-related 1-benzyl-1H-imidazole ligands and two chloride anions in a distorted octahedral geometry. Weak intermolecular C—H⋯Cl hydrogen bonds link the molecules into layers parallel to the ab plane.

In the title compound, [NiCl 2 (C 10 H 10 N 2 ) 4 ], the Ni II ion is located on an inversion center being coordinated by four N atoms from two pairs of symmetry-related 1-benzyl-1Himidazole ligands and two chloride anions in a distorted octahedral geometry. Weak intermolecular C-HÁ Á ÁCl hydrogen bonds link the molecules into layers parallel to the ab plane.

Comment
Crystal engineering, the rational design of functional molecular solids, is currently an active area of investigation because of its importance in supramolecular chemistry, materials science, and solid-state chemistry (Desiraju, 2007;Moulton & Zaworotko, 2001). It is noteworthy that a promising strategy for inorganic crystal engineering through combining non-covalent bonds such as van der Waals, π···π stacking and hydrogen bonds with coordination chemistry has attracted increasing attention in recent years (Balamurugan et al., 2004). Organic ligands are often used to coordinate to transition metals via coordinate bonds to generate metal complexes as the building blocks of the assembly. Imidazole and its derivatives are ubiquitous in biological and biochemical structure and function and thus attracted special attention in the construction of some interesting metal-organic frameworks in recent years (Huang et al., 2006;Lu et al., 2006). Here, we report the crystal structure of the title compound, (I).
In (I) (Fig. 1), each Ni II ion displays a slightly distorted octahedral coordination geometry defined by four 1-benzyl-1Himidazole ligands and two chloride anions. The Ni-N bond lengths are in the range of 2.070 (5) Å to 2.140 (3) Å and the Ni-Cl bond lengths is 2.468 (2) Å. Weak intermolecular C-H···Cl hydrogen bonds (Table 1) enhance the crystal packing stability.

Experimental
The 1-benzyl-1H-imidazole was prepared according to the literature (Owen et al., 2006). Nickel (II) chloride hexahydrate (1 mmol, 0.24 g) and 1-benzyl-1H-imidazole (4 mmol, 0.63 g) were mixed in chloroform (15 ml) and the mixture was stirred for 5 h at room temperature. After filtration, the solid was dissolved in methanol (8 ml). Green crystals suitable for X-ray analysis were obtained by slow evaporation of this solution over a period of six days.

Refinement
All H atoms were positioned geometrically with C-H = 0.93 and 0.97 Å, and refined in the riding model approximation, with U iso (H) = 1.2 U eq (C) . Fig. 1. The molecular structure of (I), showing 30% probability displacement ellipsoids and the atomic numbering. The unlabelled atoms are related with the labelled ones by symmetry element (-x, -y, -z). The most probable reason for a large number of missing reflections -238 -lies in the fact that it is very difficult to obtain high quality crystal. After we collected the reflections of the crystal, we couldn't gain perfect crystal data. To get better and reasonable structure of the crystal, those reflections which seriously influence the optimization of the crystal structure were omitted during the course of refinement of the data. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.