Tetraaquabis(2-methyl-1H-benzimidazolium-1,3-diacetato-κO)cobalt(II) tetrahydrate

In the title compound, [Co(C12H11N2O4)2(H2O)4]·4H2O, the CoII atom lies on an inversion center and is octahedrally coordinated by six O atoms from four water molecules and two monodentate zwitterionic 2-methylbenzimidazolium-1,3-diacetate ligands. An intramolecular O—H⋯O hydrogen bond occurs. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into a three-dimensional network. π–π interactions between the imidazole and benzene rings [centroid–centroid distance = 3.9031 (17) Å] consolidate the crystal packing.

In the title compound, [Co(C 12 H 11 N 2 O 4 ) 2 (H 2 O) 4 ]Á4H 2 O, the Co II atom lies on an inversion center and is octahedrally coordinated by six O atoms from four water molecules and two monodentate zwitterionic 2-methylbenzimidazolium-1,3diacetate ligands. An intramolecular O-HÁ Á ÁO hydrogen bond occurs. In the crystal, intermolecular O-HÁ Á ÁO hydrogen bonds link the molecules into a three-dimensional network.interactions between the imidazole and benzene rings [centroid-centroid distance = 3.9031 (17) Å ] consolidate the crystal packing.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HY2449).

Comment
Coordination polymers have attracted much interest due to their potential applications in many areas such as catalysis, molecular adsorption, magnetism properties and non-linear optics (Kitagawa et al., 2004;Robson, 2000). We report herein the structure of the title compound based on a flexible ligand 1-acetoxy-2-methylbenzimidazole-3-acetate acid (Lian et al., 2009).
The asymmetric unit of the title compound ( Fig. 1) contains half of the complex molecule and two uncoordinated water molecules. The Co II atom lies on an inversion center and is octahedrally coordinated by six O atoms from four water molecules and two 2-methylbenzimidazolium-1,3-diacetate ligands. In the crystal structure, intra-and intermolecular O-H···O hydrogen bonds link the molecules into a three-dimensional network (Fig. 2). π-π interactions between the imidazole and benzene rings [centroid-centroid distance = 3.9031 (17) Å] consolidate the crystal packing.

Refinement
H atoms of water molecules were located in difference Fourier maps and refined as riding atoms, with a distance restraint of O-H = 0.85 Å and U iso (H) = 1.2U eq (O). H atoms bonded to C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 (aromatic), 0.97 (methylene) and 0.96 (methyl) Å and with U iso (H) = 1.2(1.5 for methyl)U eq (C).