Crystal structure of trans-diaquabis(4-cyanobenzoato-κO)bis(nicotinamide-κN 1)cobalt(II)

In the title complex, the CoII atom is located on an inversion centre and is coordinated by two 4-cyanobenzoate (CNB) 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 sphere is completed by the two N atoms of the NA ligands in the axial positions.

In the title complex, [Co(C 8 H 4 NO 2 ) 2 (C 6 H 6 N 2 O) 2 (H 2 O) 2 ], the Co II atom is located on an inversion centre and is coordinated by two 4-cyanobenzoate (CNB) 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 sphere 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 22.11 (15) , while the pyridine and benzene rings are oriented at a dihedral angle of 89.98 (5) . In the crystal, intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the molecules, enclosing R 2 2 (8) and R 4 4 (8) ring motifs, forming layers parallel to (100). The layers are linked via C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds, resulting in a three-dimensional network. A weak C-HÁ Á Á interaction is also observed.

Chemical context
Nicotinamide (NA) is one form of niacin. A deficiency of this vitamin leads to loss of copper from the body, known as pellagra disease. Victims of pellagra show unusually high serum and urinary copper levels (Krishnamachari, 1974). The nicotinic acid derivative N,N-diethylnicotinamide (DENA) is an important respiratory stimulant (Bigoli et al., 1972). Transition metal complexes with biochemical-relevant molecules show interesting physical and/or chemical properties, through which they may find applications in biological systems (Antolini et al., 1982). Some benzoic acid derivatives, such as 4-aminobenzoic acid, have been extensively reported in coordination chemistry, as bifunctional organic ligands, due to the varieties of their coordination modes (Chen & Chen, 2002;Amiraslanov et al., 1979;Hauptmann et al., 2000).
The structure-function-coordination relationships of the arylcarboxylate ion in Zn II complexes of benzoic acid ISSN 2056-9890 derivatives change depending on the nature and position of the substituted groups on the benzene ring, the nature of the additional ligand molecule or solvent, and the pH and temperature of synthesis Nadzhafov et al., 1981;Antsyshkina et al., 1980;Adiwidjaja et al., 1978). When pyridine and its derivatives are used instead of water molecules, the structure is completely different (Catterick et al., 1974). In this context, we synthesized the Co II -containing title compound, trans-diaquabis(4-cyanobenzoato-O)bis(nicotinamide-N 1 )cobalt(II), [Co(C 8 H 4 O 2 N) 2 (C 6 H 6 N 2 O) 2 (H 2 O) 2 ], and report herein its crystal structure.

Structural commentary
In the mononuclear title complex, the Co II atom is located on an inversion centre and is coordinated by two 4-cyanobenzoate (CNB) anions, two nicotinamide (NA) ligands and two water molecules, with all ligands coordinating in a monodentate manner (Fig. 1).
The two symmetry-related carboxylate O atoms (O2 and O2 i ) and the two symmetry-related water O atoms (O4 and O4 i ) form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination sphere is completed by the two symmetry-related N atoms (N2 and N2 i ) of the two NA ligands in the axial positions [symmetry code: (i) Àx + 1, Ày + 1, Àz + 1] (Fig. 1)

trans-Diaquabis(4-cyanobenzoato-κO)bis(nicotinamide-κN 1 )cobalt(II)
Crystal data 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.