(N 4-n-Butylpyridine-4-carbothioamide-κN 4)chloridobis(dimethylglyoximato-κ2 N,N′)cobalt(III) hemihydrate

The title compound, trans-[Co(C4H7N2O2)2Cl(C10H14N2S)]·0.5H2O, contains two independent molecules in the asymmetric unit in which the CoIII ions are coordinated in slightly distorted octahedral coordination environments. The bis-chelating glyoximate ligands, which occupy equatorial sites, are linked by interligand O—H⋯O hydrogen bonds. The dihedral angles between the mean planes of the glyoximate ligands in each molecule are 2.07 (8) and 1.60 (1)°. The asymmetric unit contains a solvent water molecule which is disordered over two sites with refined occupancies 0.64 (2) and 0.36 (2).


S1. Comment
The study of simple models of the B 12 coenzyme such as the cobaloximes, [RCo(dmgH) 2 L] where R= alkyl group, dmgH -= dimethylglyoximate and L=neutral ligand, has furnished significant amounts of data that have provided a foundation for understanding the behaviour of cobaloximes (Trogler et al., 1974). Compared to other cobalamins and other model systems, cobaloximes have shorter Co-L bonds where L= pyridine or a substituted pyridine group. It is known that such a metal coenzyme is related to a number of 1,2-intramolecular rearangement enzymatic reactions (Dolphin et al., 1982).
Early X-ray diffraction analysis has shown that the coenzyme has a bulky corrin ring in the equatorial position (Bresciani-Pahor et al., 1985) the deadenosyl group and 5,6-dimethylbenzimidazole group as the axial ligands. The flexiblity of the equatorial oxime ligands is quite similar to that of corrin in neutral co-factor (Geno & Halpern, 1987). In the title compond the coordination about the Co III ion is slightly distorted octahedral with the the N-n-Butyl-4-pyridinecarbothioamide and chloride ligands occupy the axial positions and the two dimethyl glyoximato ligands occupy the equatorial sites. The axial bonds are essentially perpendicular (see coordination bond angles) to the equatorial glyoximate leastsquares planes (with maximum deviation from the planes of 0.054 (2) and 0.072 (2)Å for O3 and O8 respectively). In one molecule the n-butyl group is in an extended conformation, while in the other it has a coiled conformation as described by the torsion angles N12-C33-C34-C35 = 177.7 (4) and N6-C15-C16-C17 = -51.0 (4) °, respectively. The dihedral angle between the mean planes of the glyoximato ligands in each molecule are 2.07 (8)° and 1.60 (1)° (cf. Englert et al., 1999;2000). There is one weak C-H···Cl interaction in involving chlorine atom of one molecule and an H atom from the other independent molecule [H28···Cl1 i = 2.72Å; C28-H28-Cl1 i = 156° and C28···Cl1 i = 3.591 (4)Å; symmetry code (i): 3/2-x, -1/2+y, 1/2-z].

S2. Experimental
The title compound was synthesized by a literature method (Schrauzer & Kohnel, 1964), using H[Co(dmgH) 2 Cl 2 ] as the starting material (Ramesh et al., 2008). The dichloro cobaloxime was mixed with N-n-Bu-4-PCT in 1:1 molar ratio in about 60 ml of absolute ethanol and allowed to stir for 3hrs with warming. The resulting brown coloured complex was filtered and washed with absolute ethanol and ether and dried over vacuum desiccator. Crystals of the complex were grown in ethanol by slow evaporation. The purity of the complex was ascertained by UV-Vis, IR and NMR.

S3. Refinement
H atoms were visible in difference Fourier maps but those bonded to H atoms were placed idealized positions and included in the refinement in a riding-model approximation with C-H(aromatic) = 0.93Å and U iso (H) = 1.2U eq C; C-H(methyl) = 0.96A%, and U iso (H) = 1.5U eq C.A%. H atoms bonded to O atoms in the complex molecules were refined independently with isotropic displacement parameters. The H atoms of the disordered water atoms were not located and supporting information sup-2 . E65, m795-m796 are not included in the refinement but are however included in the molecular formula. They were not considered in the hydrogen bonding motif.

Figure 1
The asymmetric unit with 30% probability ellipsoids. Hydrogen atoms and the solvent water is omitted for clarity.
Dashed lines indicate hydrogen bonds.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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