Diaquabis(2-iodobenzoato-κO)bis(nicotinamide-κN 1)cobalt(II)

In the title complex, [Co(C7H4IO2)2(C6H6N2O)2(H2O)2], the CoII cation is located on an inversion center and is coordinated by two monodentate 2-iodobenzoate (IB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane around the CoII cation 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 22.3 (3)°, while the pyridine ring and the benzene ring are oriented at a dihedral angle of 84.59 (13)°. Intramolecular O—H⋯O hydrogen bonding occurs between the carboxylate group and coordinated water molecule. In the crystal, N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional supramolecular network.

In the title complex, [Co(C 7 H 4 IO 2 ) 2 (C 6 H 6 N 2 O) 2 (H 2 O) 2 ], the Co II cation is located on an inversion center and is coordinated by two monodentate 2-iodobenzoate (IB) anions, two nicotinamide (NA) ligands and two water molecules. The four O atoms in the equatorial plane around the Co II cation 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 22.3 (3) , while the pyridine ring and the benzene ring are oriented at a dihedral angle of 84.59 (13) . Intramolecular O-HÁ Á ÁO hydrogen bonding occurs between the carboxylate group and coordinated water molecule. In the crystal, N-HÁ Á ÁO, O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds link the molecules into a threedimensional supramolecular network.
The asymmetric unit of the title mononuclear Co II complex, (Fig. 1), contains one-half molecule. It consists of two nicotinamide (NA), two 2-iodobenzoate (IB) ligands and two coordinated water molecules, all ligands coordinating in a monodentate manner. The crystal structures of similar complexes of Cu II , Co II , Ni II , Mn II and Zn II ions, 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 symmetry related O atoms (O2, O2′, O4 and O4′) 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 symmetry related N atoms of the NA ligands (N1 and N1′) in the axial positions. The near equalities of the C1 -O1 [1.253 (6) Å] and C1-O2 [1.263 (6) Å] bonds in the carboxylate group indicate delocalized bonding arrangement, rather than localized single and double bonds. The Co-O bond lengths are 2.077 (3) Å (for benzoate oxygens) and 2.135 (4) Å (for water oxygens), and the Co-N bond length is 2.134 (4) Å, close to standard values (Allen et al., 1987).
In the crystal, intermolecular N-H···O, O-H···O and C-H···O hydrogen bonds (Table 1) link the molecules into a three-dimensional network.

Experimental
The title compound was prepared by the reaction of CoSO 4 .7H 2 O (1.406 g, 5 mmol) in H 2 O (20 ml) and NA (1.220 g, 10 mmol) in H 2 O (20 ml) with sodium 2-iodobenzoate (2.700 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 one week, giving orange 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 by constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). The highest residual electron density was found 0.87 Å from I1 and the deepest hole 1.30 Å from C5.

Figure 1
The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level [symmetry code: (′) -x, 1-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 > 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.