[N,N,N′,N′-Tetrakis(benzimidazol-2-ylmethyl)cyclohexane-1,2-diamine]nickel(II) dinitrate dihydrate

In the title compound, [Ni(C38H38N10)](NO3)2·2H2O, the NiII ion is located on a crystallographic twofold rotation axis and is in a distorted octahedral coordination environment. The crystal structure is stablized by intermolecular N—H⋯O and C—H⋯O hydrogen bonds, and weak C—H⋯π interactions. The O atoms of the unique nitrate ion are disordered over two sites with occupancies of 0.63 (1) and 0.37 (1). In addition, the O atom of the unique solvent water molecule is disorded over two sites with equal occupancies.

In the title compound, [Ni(C 38 H 38 N 10 )](NO 3 ) 2 Á2H 2 O, the Ni II ion is located on a crystallographic twofold rotation axis and is in a distorted octahedral coordination environment. The crystal structure is stablized by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, and weak C-HÁ Á Á interactions. The O atoms of the unique nitrate ion are disordered over two sites with occupancies of 0.63 (1) and 0.37 (1). In addition, the O atom of the unique solvent water molecule is disorded over two sites with equal occupancies.
Oki, A. R., Sanchez, J., Morgan, R. J. & Ngai, L. (1996) N,N,N', cyclohexane-1,2-diamine (CTB) is a polybenzimidazole ligand, which has the advantage that the basicity of the coordinating group approximates that of histidine (pKb: histidine = 7.96 and benzimidazole = 8.47;Main, 1992). Recently, studies of ligand CTB and its metal coordination compounds have been widely carried out (Li et al.,2005;Zhao et al., 2005). In a continuation of this work, the title compound, (I), was prepared as part of a series of syntheses to produce new benzimidazole derivatives. We report the crystal stucture of the title compound herein.
In the molecule structure of (I), the Ni II ion is located on a crystallographic twofold rotation axis and is is coordinated by four benzimidazolyl(bzim) N atoms and two amino N atoms of the ligand CTB, in a distorted octahedral environment ( Fig.1). The amino N atoms are slightly further away from the Ni II ion than the benzimidazolyl N atoms. The Ni-N bond lengths are similar to the values reported in a related structure (Oki et al.,1996). As shown in Fig. 2, the crystal structure is stablized by intermolecular N-H···O, C-H···O hydrogen bonds and weak C-H···π interactions.

Experimental
All reagents and solvents were used as obtained without further purification. The ligand CTB was prepared according to literature methods (Hendriks et al., 1982). Compound (I) was synthesized by refluxing stoichiometric quantities (1:1 molar ratio) of CTB (0.64 g, 1 mmol) and nickel(II) dinitrate hexahydrate (0.29 g, 1 mmol) in 95% ethanol (30 ml) at 333 K for 6 h. The solution was cooled to room temperature, filtered and evaporated to obtain the product (yield 72%). Crystals of (I) were grown from an ethanol solution by slow evaporation.

Special details
Geometry. All e.s. 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. supplementary materials sup-9