Diaqua-bis(4-bromo-2-formyl-phenolato-κO,O')cobalt(II).

In the title complex, [Co(C(7)H(4)BrO(2))(2)(H(2)O)(2)], the Co(II) ion, which lies on a crystallographic inversion center, is coordin-ated by four O atoms from two bidentate 4-bromo-2-formyl-phenolate ligands and two O atoms from two water ligands in a slightly distorted octa-hedral environment. In the crystal structure, one-dimensional chains are formed through inter-molecular O-H⋯O hydrogen bonds, which are further linked into a two-dimensional network through Br⋯Br inter-actions [Br⋯Br = 3.772 (4) Å].

In the title complex, [Co(C 7 H 4 BrO 2 ) 2 (H 2 O) 2 ], the Co II ion, which lies on a crystallographic inversion center, is coordinated by four O atoms from two bidentate 4-bromo-2formylphenolate ligands and two O atoms from two water ligands in a slightly distorted octahedral environment. In the crystal structure, one-dimensional chains are formed through intermolecular O-HÁ Á ÁO hydrogen bonds, which are further linked into a two-dimensional network through BrÁ Á ÁBr interactions [BrÁ Á ÁBr = 3.772 (4) Å ].

Comment
Halogens have a ubiquitous presence in both inorganic and organic chemistry. Schiff bases of bromo substituents on aromatic groups have aroused increasing interest in recent years because these halogenated compounds are an attractive target for use in supramolecular chemistry and crystal engineering wherein the halogen atoms are directly involved in forming intermolecular interactions (Cohen et al., 1964, Zordan et al., 2005Desiraju, et al. 1989, Zaman et al., 2004Zhang, et al., 2007, Chen, et al., 2008. The title compound, (I), contains the bromo ligand 5-bromo-2-hydroxy-benzaldehyde, with one Br atom accessible at the periphery of each ligand.

Experimental
Distilled water (30 ml) containing 5-bromo-2-hydroxy-benzaldehyde (0.201 g, 1 mmol) was dropwise added to an aqueous solution containing amino-methanesulfonic acid (0.111 g, 1 mmol) and sodium hydroxide (0.040 g, 1 mmol) with stirred during 10 min. After stirring for 1 h, an aqueous solution of cobalt chloride (0.237 g, 1 mmol) was added to the resulting solution and stirred for 2 h and filtrate. the filtration was left to stand at room temperature. After 12 days, red crystals were produced from the filtrate (yield: 76.4 %, based on Co).

Refinement
H atoms were positioned geometrically and were treated as riding atoms, with C-H distances of 0.93 Å and U iso (H) = 1.2 U eq (C), and with and O-H distance of 0.85 Å and U iso (H) = 1.5 U eq (O) .

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.

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