Chloridobis(dimethylglyoximato-κ2 N,N′)(4-methylpyridine-κN)cobalt(III) hemihydrate

In the title complex, [Co(C4H7N2O2)2Cl(C6H7N)]·0.5H2O, the central CoIII ion, chelated by four N atoms of the two bidenate glyoximate ligands, exhibits a slightly distorted octahedral geometry. The axial positions are occupied by a chloride ion and the 4-methylpyridine N atom. Intermolecular O—H⋯O hydrogen bonds link the molecules in the crystal via the water molecules, while the glyoximate ligands exhibit intramolecular O—H⋯O hydrogen bonds.

In the title complex, [Co(C 4 H 7 N 2 O 2 ) 2 Cl(C 6 H 7 N)]Á0.5H 2 O, the central Co III ion, chelated by four N atoms of the two bidenate glyoximate ligands, exhibits a slightly distorted octahedral geometry. The axial positions are occupied by a chloride ion and the 4-methylpyridine N atom. Intermolecular O-HÁ Á ÁO hydrogen bonds link the molecules in the crystal via the water molecules, while the glyoximate ligands exhibit intramolecular O-HÁ Á ÁO hydrogen bonds.

Experimental
Crystal data [Co(C 4

Comment
Cobaloximes have been used extensively as structural and functional mimics for vitamin-B 12 (Brown, 2005 andRandaccio et al., 1989).Their chemical properties have been widely studied (Schrauzer et al.,1966).The two aspects of cobaloxime chemistry are their (a) inertness with respect to ligand exchange making them to serve as ideal system for studies relating to electron transfer reactions and (b)crystal parameters.The distance between glyoximato oxygen atoms in these complexes amount to 2.4-2.6 Å, a distance range of considerable interest for strong intra molecular hydrogen bonding (Reemers et al., 2002).Compared to cobalamins, cobaloximes have shorter Co-N axial bond distance. It is known that coenzymes are related to number of 1,2-intra molecular rearrangement reactions (Dolphin et al.,1982).Most of the recent studies on cobaloximes have been focused on their structure-property relationships (Gupta et al., 2004 andDutta et al., 2009).
In this title complex, the coordination about the Co III ion is slightly distorted octahedral (Revathi et al., 2009 andKavitha et al., 2008)

Experimental
The complex was prepared by the literature method (Schrauzer et al.,1966) using H[Co(dmgH) 2 Cl 2 ] as the starting material (Ramesh et al.,2008). The dichloro cobaloxime was mixed with 4-methylpyridine in 1:1 molar ratio in about 60 ml of ethanol and allowed to stir for 3 hrs. The resulting brown coloured complex was filtered,washed with absolute ethanol followed by ether and dried over vacuum desicator. Crystals of the complex were grown in ethanol by slow evaporation method. The complex was characterized by UV, IR and H 1 NMR spectra. A moderately intense band around 250 nm may be ascribed to π-π* transition of the dmgHgroup. A shoulder around 330 nm may be due to the ligand to metal charge transfer transition, LMCT (Dayalan et al., 2001). The C=N stretching vibration of the oxime in its complex was observed at 1580 cm -1 and the intra molecular hydrogen bonded -OH around 3450 cm -1 . A moderate peak at 1094 cm -1 may be assigned to the C=N-O stretching of the oxime. The peak at 513 cm -1 could be attributed to cobalt(III)-nitrogen stretching (Bline et al.,1958 All the hydrogen atoms were identified from the difference electron density peak and fixed accordingly. The H atom bound to methyl C atoms were constrained to riding atoms wit d(C-H) = 0.96Å and U iso (H) = 1.5U equ (C). and the hydrogen atoms bound to aromatic carbon were constrained to riding atoms with d(C-H) = 0.93Å and U iso (H) =1.2U equ (C).The posotion of the hydrogen atom bound to the hydroxyl group was identified from the difference in the electron density map and restrained to a distance of d(O2-H2) = 0.90 (1) Å. The lattice solvent water O5 is left as anisotropically refined without the hydrogen being fixed but the water hydrogen is included in the chemical formula.
Figures Fig. 1. The ORTEP representation of the complex drawn at 30% probability level with the atom labelling scheme.