Diaquabis(2-chlorobenzoato-κO)bis(nicotinamide-κN 1)cobalt(II)

In the title complex, [Co(C7H4ClO2)2(C6H6N2O)2(H2O)2], the CoII cation is located on an inversion center and is coordinated by two 2-chlorobenzoate anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane around the CoII cation form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two pyridine N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the adjacent benzene ring is 29.7 (4)°, while the pyridine and benzene rings are oriented at a dihedral angle of 83.17 (15)°. Intramolecular O—H⋯O hydrogen bonding occurs between the carboxylate group and coordinating water molecule. In the crystal, intermolecular N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional network.

The title compound, (I), is a mononuclear complex, where the Co II ion is located on a crystallographic inversion center.
The asymmetric unit contains one 2-chlorobenzoate (CB) anion, one nicotinamide (NA) ligand and one coordinated water molecule, all ligands are monodentate (Fig. 1) In the title complex, the four symmetry related O atoms (O2, O2′, O4 and O4′) in the equatorial plane around the Co II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two symmetry related N atoms of the NA ligands (N1 and N1′) in the axial positions (Fig. 1).
In the crystal structure, intermolecular N-H···O, O-H···O and weak C-H···O hydrogen bonds (Table 1) link the molecules into a three-dimensional supramolecular network.

Experimental
The title compound was prepared by the reaction of CoSO 4 .7H 2 O (1.40 g, 5 mmol) in H 2 O (40 ml) and nicotinamide (1.78 g, 10 mmol) in H 2 O (20 ml) with sodium 2-chlorobenzoate (2.23 g, 10 mmol) in H 2 O (50 ml). The mixture was filtered and set aside to crystallize at ambient temperature for two weeks, giving pink single crystals (yield; 3.065 g,

Refinement
Atoms H21, H22 (for NH 2 ) and H41, H42 (for H 2 O) were located in a difference Fourier map and refined isotropically.
The C-bound H-atoms were positioned geometrically with C-H = 0.93 Å for aromatic H atoms and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). The highest residual electron density was found 1.17 Å from Co1 and the deepest hole 0.80 Å from Co1.

Figure 1
The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Primed atoms are generated by the symmetry operator: (′) 1-x, -y, -z. Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.