Aquachloridobis(diphenylglyoximato-κ2 N,N′)cobalt(III) dihydrate

The asymmetric unit of the title complex, [Co(C14H11N2O2)2Cl(H2O)]·2H2O or [Co(dpgH)2Cl(H2O)]·2H2O, where dpgH− is diphenyl glyoximate, consists of one-half of a [Co(dpgH)2Cl(H2O)] complex and one solvent water molecule. The complex is completed through inversion symmetry, with the CoIII atom situated at the centre of symmetry. The coordination geometry around the CoIII atom is distorted octahedral with the four N atoms of the two dpgH− ligands forming an approximate square plane with N—Co—N bite angles of 81.13 (14) and 98.87 (14)°. The Cl− ligand and the water molecule are disordered in a 1:1 ratio and are in the axial positions, almost perpendicular to the plane of the glyoximate ligands [O—Co—Cl = 175.3 (10)°]. The two glyoximate ligands are linked by strong intramolecular O—H⋯O hydrogen bonds. In addition, O—H⋯O interactions involving the solvent water molecules and O—H⋯N hydrogen-bonding interactions are also observed. The solvent water molecule is disordered over five positions with different occupancies.

The asymmetric unit of the title complex,  O 2 ) 2 Cl(H 2 O)]Á2H 2 O or [Co(dpgH) 2 Cl(H 2 O)]Á2H 2 O, where dpgH À is diphenyl glyoximate, consists of one-half of a [Co(dpgH) 2 Cl(H 2 O)] complex and one solvent water molecule. The complex is completed through inversion symmetry, with the Co III atom situated at the centre of symmetry. The coordination geometry around the Co III atom is distorted octahedral with the four N atoms of the two dpgH À ligands forming an approximate square plane with N-Co-N bite angles of 81.13 (14) and 98.87 (14) . The Cl À ligand and the water molecule are disordered in a 1:1 ratio and are in the axial positions, almost perpendicular to the plane of the glyoximate ligands  ]. The two glyoximate ligands are linked by strong intramolecular O-HÁ Á ÁO hydrogen bonds. In addition, O-HÁ Á ÁO interactions involving the solvent water molecules and O-HÁ Á ÁN hydrogen-bonding interactions are also observed. The solvent water molecule is disordered over five positions with different occupancies.

Comment
The dioxime complexes of cobalt(III), known as cobaloximes, and their derivatives have been found to mimic vitamin-B 12 coenzyme. The studies on steric and electronic effects of cobaloximes helped in the successful design of novel derivatives with desired properties (Gupta et al., 2003;Randaccio, 1999;Brown & Satyanarayana, 1992;Gilaberte et al., 1988). Among the stereoisomeric benzildioximes (syn, amphi, anti), only the anti isomer shows chelation properties towards transition metal ions (Varhelyi et al., 1999).
In the structure of the title compound, [Co(C 14   The two glyoximate ligands are linked by strong intramolecular O-H···O hydrogen bonds. In addition, O1-H1···N2 hydrogen bonding interaction is also observed (Fig. 2). A similar interaction was observed for a related complex (Meera et al., 2009). The lattice water molecule (O4) is disordered over five positions with different occupancies. Although the H positions of the disordered water molecules could not be located, close O···O interactions suggest likewise an involvement in hydrogen bonding (Table 2).

Experimental
Cobalt(II) chloride hexahydrate was thoroughly ground and mixed with diphenylglyoxime in a 1:2 molar ratio in an aqueous solution of acetone. The reaction mixture was stirred for five hours at an elevated temperature (Toscano et al., 1983;Gupta et al., 2001). The resulting brown mass was filtered, washed with acetone, ether and dried in a desiccator. Brown coloured crystals appeared in two to three days on slow evaporation of the saturated solution of the complex in ethanol. Elemental analysis, obtained by analytical method, agreed well with the theoretical data expected for the formula of the complex, C 28 H 28 N 4 O 7 ClCo. Anal., % (calc., %): C 53.97 (53.58); H 4.94 (4.47); N 9.05 (8.93). The C═N stretching vibration of oxime in its complex was observed at 1385 cm -1 and the intramolecular hydrogen bonded -OH around 3140 cm -1 . A moderate peak around 1090 cm -1 may be assigned to the C=N-O stretching of the oxime. The band around 540 cm -1 could be attributed to cobalt(III)-nitrogen stretching. The 1 H NMR spectrum of the complex in acetone-d 6 shows three different signals corresponding to the three different aromatic protons of the diphenylglyoximate (Gupta et al., 2004;Lopez et al., 1992). The H atoms in the second and the sixth position of the benzene ring of the diphenylglyoximate show a doublet at 7.2 p.p.m., while the third and fifth H atoms show a triplet at 7.4 p.p.m.. Similarly, the fourth one gives a triplet at 7.3 p.p.m..The supplementary materials sup-2 oxime -OH protons resonate at 9.1 p.p.m.. A singlet around 8.5 p.p.m. represents the protons of the -OH group of the aqua ligand (Silverstein & Bassler, 1984;Mandal & Gupta, 2005).

Refinement
The