Aquabromidobis(dimethylglyoximato)cobalt(III)

In the title complex, [CoBr(C4H7N2O2)2(H2O)], a crystallographic mirror plane bisects the molecule, perpendicular to the glyoximate ligands. The geometry around the cobalt(III) atom is approximately octahedral with the four glyoximate N atoms forming the square base. A bromide ion and the O atom of a water molecule occupy the remaining coordination sites. The N—Co—N bite angles are 82.18 (4) and 80.03 (16)°. The glyoximate moieties form strong intramolecular O—H⋯O hydrogen bonds. The coordinated water molecule forms an intermolecular O—H⋯O hydrogen bond with a glyoximate O atom, thereby generating supramolecular chains parallel to [010].

In the title complex, [CoBr(C 4 H 7 N 2 O 2 ) 2 (H 2 O)], a crystallographic mirror plane bisects the molecule, perpendicular to the glyoximate ligands. The geometry around the cobalt(III) atom is approximately octahedral with the four glyoximate N atoms forming the square base. A bromide ion and the O atom of a water molecule occupy the remaining coordination sites. The N-Co-N bite angles are 82.18 (4) and 80.03 (16) . The glyoximate moieties form strong intramolecular O-HÁ Á ÁO hydrogen bonds. The coordinated water molecule forms an intermolecular O-HÁ Á ÁO hydrogen bond with a glyoximate O atom, thereby generating supramolecular chains parallel to [010].
Cobalt(III) complexes, being low spin, are conveniently studied in aqueous medium (Randall & Alberty, 1970). We report here the synthesis and X-ray crystal structure of the title compound.
The structure is further stabilized through van der waals interaction.

Experimental
Cobalt(II) bromide hexahydrate was thoroughly grinded and exposed to microwave for 30 s.The dehydrated cobalt(II) bromide was mixed with dimethylglyoxime in 1:2 molar ratio in acetone medium and allowed to stir for an hour (Vijayraghavan & Dayalan, 1992). The dibromo complex obtained was filtered dried and then it was refluxed with water for two hours. The of oxime in its complex was observed at 1580 cm -1 and the intra molecular hydrogen bonded OH around 3100 cm -1 . A moderate peak around 1070 cm -1 may be assigned to the C=N-O stretching of the oxime. The peak around 510 cm -1 could be attributed to cobalt(III)-nitrogen stretching (Khan et al., 1997;Folgando et al., 1986). The 1 H NMR spectra of the supplementary materials sup-2 complex in DMSO-d 6 shows a sharp intense singlet at 2.3 p.p.m. corresponding to methyl protons of the oxime.The oxime -OH resonates at 13.08 p.p.m..A singlet around 8.5 ppm represents the -OH of the aquo ligand (Lopez et al., 1986).

Refinement
The H-atoms bound to C-atoms were constrained to riding atoms with d(C-H) = 0.96Å and U iso (H) = 1.5U equ (C).The positions of the hydrogen atoms,bound to the glyoximate and water O atoms, were identified from difference in the electron density map and restrained to a distance of d(O2-H2) = 0.92 (1)Å and d(O3-H3) = 0.85 (1) Å. A difference elctron density peak of 1.008 e A -3 was observed after the final refinement. Since the observed peak position is meaningless it is ignored. Figures   Fig. 1. Displacement ellipsoid plot of the title compound drawn at 30% probability level.The equivalent symbol i represents the mirror symmetry (x, 1/2; -y,z) at one fourth of b axes.