Diaquabis(5-carboxy-2-propyl-1H-imidazole-4-carboxylato-κ2 N 3,O 4)cobalt(II) 3.5-hydrate

In the title complex, [Co(C8H9N2O4)2(H2O)2]·3.5H2O, the CoII cation is six-coordinated by two H2pimda− ligands (H3pimda is 2-propyl-1H-imidazole-4,5-carboxylic acid) and two water molecules in a distorted octahedral environment. The crystal structures features a three-dimensional network stabilized by extensive O—H⋯O and N—H⋯O hydrogen bonds. The propyl groups of the ligands are disordered over two sets of sites with refined occupancies of 0.673 (8):0.327 (8) and 0.621 (17):0.379 (17). One of the water molecules is located on a site with half-occupancy.

In the title complex, [Co(C 8 H 9 N 2 O 4 ) 2 (H 2 O) 2 ]Á3.5H 2 O, the Co II cation is six-coordinated by two H 2 pimda À ligands (H 3 pimda is 2-propyl-1H-imidazole-4,5-carboxylic acid) and two water molecules in a distorted octahedral environment. The crystal structures features a three-dimensional network stabilized by extensive O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds. The propyl groups of the ligands are disordered over two sets of sites with refined occupancies of 0.673 (8):0.327 (8) and 0.621 (17):0.379 (17). One of the water molecules is located on a site with half-occupancy.
As illustrated in figure 1, the title complex molecule is isomorphous with Ni(II), Mn(II), Cd(II) and Zn(II) analogues (Fan et al., 2010;Li, Dong et al., 2010;Li, Miao et al., 2010), Similar structural description applies to the present isomorphous complex. The Co II is six-coordinated in a distorted octahedral geometry. the H 3 pimda acts as a bidentate mode to chelate the center Co(II). one carboxy group of the ligand was delocalized and the other was protonated, indicated by the difference of the bond lengths. The dihedral angle between the two imidazole rings is 84.2 (2) %A. In the crystal structure, the three-dimensional supramolecular framework is stabilized by extensive O-H···O and N-H···O hydrogen bonds.The propyl groups of H 3 pimda are disordered over two sets of sites with refined occupiencies of 0.673 (8):0.327 (8) and 0.621 (17): 0.379 (17). One of the water molecules is half occupied.

Experimental
A mixture of Co(NO 3 ) 2 (0.5 mmol, 0.06 g) and 2-propyl-1H-imidazole-4,5-dicarboxylic acid(0.5 mmol, 0.99 g) in 15 ml of H 2 O solution was sealed in an autoclave equipped with a Teflon liner (20 ml) and then heated at 433K for 4 days. Crystals of the title compound were obtained by slow evaporation of the solvent at room temperature.

Refinement
Water H atoms were located in a difference Fourier map and were allowed to ride on the parent atom, with U iso (H) = 1.5U eq (O). Carboxyl H atoms were located in a difference map and refined with distance restraints, U iso (H) = 1.5U eq (O).
Other H atoms were placed at calculated positions and were treated as riding on parent atoms with C-H = 0.96 (methyl), 0.97 (methylene) and N-H = 0.86 Å, U iso (H) = 1.2 or 1.5U eq (C,N). The propyl groups of H 3 pimda are disordered over two sites with refined occupancies of 0.673 (8) for the disordered components. The O3W water molecule is located close to an inversion centre, its occupancy factor was refined to 0.49 (1) and was fixed as 0.5 at the final refinements. Fig. 1. The structure of the title compound, showing the atomic numbering scheme. Non-H atoms are shown with 30% probability displacement ellipsoids.  (7) 121.