Diaquabis(3-chlorobenzoato-κO)bis(nicotinamide-κN 1)cobalt(II)

In the title complex, [Co(C7H4ClO2)2(C6H6N2O)2(H2O)2], the CoII atom is located on an inversion center and is coordinated by two 3-chlorobenzoate (CB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the adjacent benzene ring is 9.14 (9)°, while the pyridine and benzene rings are oriented at a dihedral angle of 82.18 (8)°. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds link the molecules into a two-dimensional network lying parallel to (101). π–π stacking between parallel pyridine rings of adjacent molecules [centroid–centroid distance = 3.7765 (8) Å] further stabilizes the crystal structure.

In the title complex, [Co(C 7 H 4 ClO 2 ) 2 (C 6 H 6 N 2 O) 2 (H 2 O) 2 ], the Co II atom is located on an inversion center and is coordinated by two 3-chlorobenzoate (CB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the NA ligands in the axial positions. The dihedral angle between the carboxylate group and the adjacent benzene ring is 9.14 (9) , while the pyridine and benzene rings are oriented at a dihedral angle of 82.18 (8) . In the crystal, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the molecules into a two-dimensional network lying parallel to (101).stacking between parallel pyridine rings of adjacent molecules [centroid-centroid distance = 3.7765 (8) Å ] further stabilizes the crystal structure.
In the title mononuclear complex, Co II atom is located on an inversion center and is coordinated by two 3-chlorobenzoate (CB) anions, two nicotinamide (NA) ligands and two water molecules, all ligands coordinating in a monodentate manner (Fig. 1). The crystal structures of similar complexes of Cu II , Co II , Ni II , Mn II and Zn II ions, are 2.0592 (10) Å (for benzoate oxygens) and 2.1385 (10) Å (for water oxygens), and the Co-N bond length is 2.1641 (11) Å, close to standard values (Allen et al., 1987). The Co atom is displaced out of the mean-plane of the carboxylate group (O1/C1/O2) by -0.5077 (1) Å. The dihedral angle between the planar carboxylate group and the adjacent benzene ring (C2-C7) is 9.14 (9)°. The benzene (C2-C7) and the pyridine (N1/C8-C12) rings are oriented at a dihedral angle of 82.18 (8)°.
In the crystal, N-H···O and O-H···O hydrogen bonds (Table 1)  temperature. The mixture was filtered and set aside to crystallize at ambient temperature for several days, giving pink single crystals.

Refinement
Atoms H21 and H22 (for NH 2 ) and H41 and H42 (for H 2 O) were located in a difference Fourier map and were refined freely. 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) = 1.2 × U eq (C).

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level [symmetry code: (a) -x, -y, -z]. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.32 e Å −3 Δρ min = −0.33 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0334 (17) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq  (2)