Bis[2-(1H-benzimidazol-2-yl)acetato-κ(2) N (3),O]bis-(ethanol-κO)nickel(II).

In the title compound, [Ni(C9H7N2O2)2(C2H5OH)2], the Ni(II) ion is situated on an inversion center and is coordinated by two N and two O atoms from two 2-(1H-benzimidazol-2-yl)acetate (L) ligands and by two O atoms from two ethanol ligands in a distorted octa-hedral geometry. In the L ligand, the acetate group deviates significantly from the benzimidazole plane, the C-C-C-O(coordinating) torsion angle being 34.2 (5)°. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into a two-dimensional supra-molecular network parallel to the bc plane.

In the title compound, [Ni(C 9 H 7 N 2 O 2 ) 2 (C 2 H 5 OH) 2 ], the Ni II ion is situated on an inversion center and is coordinated by two N and two O atoms from two 2-(1H-benzimidazol-2yl)acetate (L) ligands and by two O atoms from two ethanol ligands in a distorted octahedral geometry. In the L ligand, the acetate group deviates significantly from the benzimidazole plane, the C-C-C-O(coordinating) torsion angle being 34.2 (5) . In the crystal, O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds link the molecules into a two-dimensional supramolecular network parallel to the bc plane.

Experimental
Crystal data [Ni(C 9 Table 1 Hydrogen-bond geometry (Å , ).  (Chen et al., 2010;Gao et al., 2011;Guo et al., 2007;Peng et al., 2010). The main reason is that they have various coordination modes and can form high-dimensional polymers through hydrogen-bonding interactions in the process of self-assembly. In this work, we chose 2-(1H-benzimidazol-2-yl)acetic acid (HL), which contains two N atoms of an imidazole group and one carboxylate group, as the building block to prepare new metal coordination polymers. To date, only three mononuclear complexes based on the HL ligand have been reported (Chen et al.,2010). In this paper, we report the synthesis and structure of the title compound, (I), obtained by the solvothermal reaction of NiCl 2 and HL ligand.
In (I) (Fig. 1), the Ni(II) ion is coordinated by two N and two O atoms from two bidentate chelating L ligands and two O atoms from two ethanol molecules in a distorted octahedral geometry. The Ni-N bond length is equal to 2.055 (3) Å, and the Ni-O distances vary from 2.037 (3) to 2.107 (2) Å. In the crystal, intermolecular O-H···O and N-H···O hydrogen bonds (Table1) involving the carboxylate O atoms, the imidazole N atoms and the coordinated ethanol O atoms link the molecules into a two-dimensional supramolecular network parallel to the bc plane (Fig. 2).

Experimental
A mixture of NiCl 2 (0.40 mmol), HL (0.40 mmol) and 8 ml C 2 H 5 OH was sealed into a 15 ml Teflon-lined stainless steel autoclave and then heated at 373 K for 72 h under autogenous pressure. After cooling to room temperature at a rate of 2 K /h, green block crystals of the title compound suitable for X-ray diffraction were obtained (yield: 35%).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.