Tetraaquabis(1H-benzimidazole-5,6-dicarboxylato-κN 3)cobalt(II) dimethylformamide disolvate dihydrate

In the mononuclear title compound, [Co(C9H4N2O4)2(H2O)4]·2C3H7NO·2H2O, the CoII atom, which lies on a center of inversion, is coordinated by four water molecules and two N atoms from two two symmetry-related 1H-benzimidazole-5,6-dicarboxylate ligands in a distorted octahedral geometry. The packing is governed by intermolecular O—H⋯O and N—H⋯O hydrogen-bonding interactions.

In the mononuclear title compound, [Co(C 9 H 4 N 2 O 4 ) 2 -(H 2 O) 4 ]Á2C 3 H 7 NOÁ2H 2 O, the Co II atom, which lies on a center of inversion, is coordinated by four water molecules and two N atoms from two two symmetry-related 1Hbenzimidazole-5,6-dicarboxylate ligands in a distorted octahedral geometry. The packing is governed by intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen-bonding interactions.

catena-Poly
As shown in Figure 1, the Co II atom exhibits an octahedral coordination sphere, defined by two N atoms from two different 1H-benzimidazole-5,6-dicarboxylate ligands, and four water molecules. The equatorial plane is defined by O1w, O2w, O1w i and O2w i atoms, while N1 and N1 i occupy the axial position (symmetry codes: i = -x, 1 -y, 1 -z). The solvent (water and dimethylformamide) molecules are also present in the asymmetic unit. Inter/intramolecular O-H···O and N-H···O hydrogen bonds form a three-dimensional supramolecular network making the structure more stable (Fig 2).The hydrogen bonds are in the normal range (Table 1).

Experimental
A C 3 H 7 NO solution (20 mL)containing Co(NO 3 ) 2 (0.1 mmol)and 1H-benzimidazole-5,6-dicarboxylic acid(0.2 mmol) was stirred for a few minutes in air,and left to stand at room temperature for about a few weeks, then the red crystals were obtained.

Refinement
Carbon and nitrogen bound H atoms were placed at calculated positions and were treated as riding on the parent C or N atoms with C-H = 0.93 Å, N-H = 0.86 Å, and with U iso (H) = 1.2 U eq (C, N). The water H-atoms were located in a difference map, and were refined with a distance restraint of O-H = 0.84 Å; their U iso values were refined.

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.