Diaquabis(N,N-diethylnicotinamide-κN 1)bis(4-methylbenzoato-κO)cobalt(II)

In the centrosymmetric mononuclear title complex, [Co(C8H7O2)2(C10H14N2O)2(H2O)2], the CoII ion is located on an inversion center. The asymmetric unit contains one 4-methylbenzoate (PMB) anion, one N,N-diethylnicotinamide (DENA) ligand and one coordinated water molecule. The four O atoms in the equatorial plane around the CoII ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two pyridine N atoms of the DENA ligands in the axial positions. The dihedral angle between the carboxylate group and the attached benzene ring is 3.73 (14)°, while the pyridine and benzene rings are oriented at a dihedral angle of 77.28 (6)°. In the crystal structure, intermolecular O—H⋯O and C—H⋯O hydrogen bonds link the molecules into a two-dimensional network parallel to (001). The structure is further stabilized by π–π contacts between the pyridine rings [centroid–centroid distance = 3.544 (1) Å] and weak C—H⋯π interactions involving the benzene ring.

In the centrosymmetric mononuclear title complex, [Co(C 8 H 7 O 2 ) 2 (C 10 H 14 N 2 O) 2 (H 2 O) 2 ], the Co II ion is located on an inversion center. The asymmetric unit contains one 4methylbenzoate (PMB) anion, one N,N-diethylnicotinamide (DENA) ligand and one coordinated water molecule. The four O atoms 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 pyridine N atoms of the DENA ligands in the axial positions. The dihedral angle between the carboxylate group and the attached benzene ring is 3.73 (14) , while the pyridine and benzene rings are oriented at a dihedral angle of 77.28 (6) . In the crystal structure, intermolecular O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link the molecules into a twodimensional network parallel to (001). The structure is further stabilized bycontacts between the pyridine rings [centroid-centroid distance = 3.544 (1) Å ] and weak C-HÁ Á Á interactions involving the benzene ring.

Experimental
The title compound was prepared by the reaction of CoSO 4 .7H 2 O (1.41 g, 5 mmol) in H 2 O (40 ml) and DENA (1.78 g, 10 mmol) in H 2 O (10 ml) with sodium 4-methylbenzoate (1.58 g, 10 mmol) in H 2 O (300 ml). The mixture was filtered and set aside to crystallize at ambient temperature for one week, giving pink single crystals.
supplementary materials sup-2 Refinement Water H atoms (H41 and H42) were located in a difference Fourier map and refined with O-H and H···H distance restraints of 0.95 (2) Å and 1.46 (4) Å, respectively. The remaining H atoms were positioned geometrically with C-H = 0.93, 0.97 and 0.96 Å for aromatic, methylene and methyl H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for all other H atoms. Fig. 1. The molecular structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Primed atoms are generated by the symmetry operator:(') -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 > 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.

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