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

The title CoII complex, [Co(C9H9O2)2(C10H14N2O)2(H2O)2], contains two 4-ethylbenzoate (PEB), two monodentate diethylnicotinamide (DENA) ligands and two water molecules. 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 N atoms of the DENA ligands in the axial positions. Intramolecular O—H⋯O hydrogen bonds link the water molecules to the carboxylate groups. The dihedral angles between the carboxylate groups and the adjacent benzene rings are 4.52 (18) and 4.56 (18)°, while the pyridine rings and the benzene rings are oriented at dihedral angles of 7.76 (10) and 5.67 (13)°. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into chains propagating along [010]. C—H⋯O interactions and a π–π contact between the pyridine rings [centroid–centroid distance = 3.476 (2) Å] are also observed.


metal-organic compounds
Özbek, B. Tercan and T. Hökelek Comment As a part of our ongoing investigations of transition metal complexes of nicotinamide (NA), one form of niacin (Krishnamachari, 1974), and/or the nicotinic acid derivative N,N-diethylnicotinamide (DENA), an important respiratory stimulant (Bigoli et al., 1972), the title compound was synthesized and its crystal structure is reported on herein.
The title mononuclear Co II complex, (Fig. 1) (Hökelek et al., 2009b), have also been reported. In the copper(II) complex mentioned above the two benzoate ions coordinate to the Cu II atom as bidentate ligands, while in the other structures all the ligands coordinate in a monodentate manner.
In the title complex, the four O atoms (O1, O3, O7 and O8) 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 N atoms of the DENA ligands (N1 and N3) in the axial positions. Intramolecular O-H···O hydrogen bonds link the water molecules to the carboxylate groups (Table 1 and (Table   1 and Fig. 2). There also exist C-H···O interactions leading to the formation of two-dimensional networks lying parallel to (110). The π-π contact between the pyridine rings, Cg3-Cg4 i , may further stabilize the crystal structure [centroid-tocentroid distance = 3.476 (2) Å; symmetry code: (i) x -1, y, z; Cg3 and Cg4 are the centroids of the rings C (N1/C19-C23) and D (N3/C29-C33), respectively].

supplementary materials sup-2 Experimental
The title compound was prepared by the reaction of CoSO 4 .7H 2 O (1.40 g, 5 mmol) in H 2 O (100 ml) and N,N-diethylnicotinamide (1.78 g, 10 mmol) in H 2 O (50 ml) with sodium 4-ethylbenzoate (1.72 g, 10 mmol) in H 2 O (100 ml) at room temperature. The mixture was filtered and set aside to crystallize at ambient temperature for four days, giving pink single crystals.

Refinement
The compound crystallized as an inversion twin: refined BASF parameter = 0.371 (13), for 2995 Friedel pairs (88.2% coverage). The H-atoms of the water molecules (H71, H72, H81 and H82) were located in a difference Fourier map and were freely refined. The C-bound 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) = k × U eq (C), where k = 1.5 for methyl H-atoms and k = 1.2 for all other H-atoms.   Table 1 for details; H-atoms not involved in hydrogen bonding have been omitted for clarity].

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.