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

In the crystal structure of the title CoII complex, [Co(C8H5O3)2(C10H14N2O)2(H2O)2], the metal centre is located on an inversion center and is coordinated by two 4-formylbenzoate (FOB), two diethylnicotinamide (DENA) ligands and two water molecules in a slightly distorted CoO4N2 octahedral geometry. In the crystal structure, O—H⋯O hydrogen bonds link the molecules into infinite chains. π–π contacts between the parallel pyridine rings of neighboring DENA ligands [centroid–centroid distance = 3.652 (3) Å] further stabilize the crystal structure.

In the crystal structure of the title Co II complex, [Co(C 8 H 5 O 3 ) 2 (C 10 H 14 N 2 O) 2 (H 2 O) 2 ], the metal centre is located on an inversion center and is coordinated by two 4formylbenzoate (FOB), two diethylnicotinamide (DENA) ligands and two water molecules in a slightly distorted CoO 4 N 2 octahedral geometry. In the crystal structure, O-HÁ Á ÁO hydrogen bonds link the molecules into infinite chains.

Experimental
Crystal data [Co(C 8

S1. Comment
Transition metal complexes with biochemically active ligands frequently show interesting physical and/or chemical properties, as a result they may find applications in biological systems (Antolini et al., 1982). The structural functions and coordination relationships of the arylcarboxylate ion in transition metal complexes of benzoic acid derivatives change depending on the nature and position of the substituent groups on the benzene ring, the nature of the additional ligand molecule or solvent, and the medium of the synthesis (Nadzhafov et al., 1981;Shnulin et al., 1981). The nicotinic acid derivative N,N-diethylnicotinamide (DENA) is an important respiratory stimulant (Bigoli et al., 1972).
The structure determination of the title compound, (I), a cobalt complex with two formylbenzoate (FOB), two diethylnicotinamide (DENA) ligands and two water molecules, was undertaken in order to determine the properties of the ligands and also to compare the results obtained with those reported previously.
Compound (I) is a monomeric complex, with the Co atom on a centre of symmetry. It contains two FOB, two DENA ligands and two water molecules (Fig. 1). All ligands are monodentate. The four O atoms (O1, O5, and the symmetryrelated atoms, O1′, O5′) in the equatorial plane around the Co atom 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, N1′) in the axial positions (Table 1 and  In the crystal structure, intermolecular O-H···O hydrogen bonds (Table 1)

S2. Experimental
The title compound was prepared by the reaction of CoSO 4 .H 2 O (1.73 g, 10 mmol) in H 2 O (50 ml) and DENA (3.56 g, 20 mmol) in H 2 O (15 ml) with sodium 4-formylbenzoate (3.44 g, 20 mmol) in H 2 O (50 ml). The mixture was filtered and set aside to crystallize at ambient temperature for several days, giving red single crystals.

S3. Refinement
H atoms of water molecule and formyl group were located in difference Fourier maps and refined isotropically, with restrains of O5-H51 = 0.94 (4)

Diaquabis(N,N-diethylnicotinamide-κN 1 )bis(4-formylbenzoato-κO)cobalt(II)
Crystal data Primary atom site location: structure-invariant direct methods Secondary atom site location: difference Fourier map Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o 2 ) + (0.0999P) 2 + 0.5936P] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.02 e Å −3 Δρ min = −0.33 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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  (11)