Chloridobis(dimethylglyoximato-κ2 N,N′)(ethyl pyridine-3-carboxylate-κN)cobalt(III)

In the title compound, [Co(C4H7N2O2)2Cl(C8H9NO2)], which was prepared as a model complex of vitamin B12, the CoIII atom, which is linked to four N atoms of the pseudo-macrocyclic (dmgH)2 ligand (dmgH is dimethylglyoximate) in the equatorial plane and one Cl− anion and one N atom of ethyl nicotinate in apical positions, displays an approximately octahedral coordination. The Co atom is 0.0187 (8) Å out of the mean plane of the four equatorial N atoms. The structure has an O⋯H⋯O bridge, which is very common in cobaloxime derivatives, with O⋯H distances of 1.24 (2) and 1.25 (2) Å.

In the title compound, [Co(C 4 H 7 N 2 O 2 ) 2 Cl(C 8 H 9 NO 2 )], which was prepared as a model complex of vitamin B 12 , the Co III atom, which is linked to four N atoms of the pseudomacrocyclic (dmgH) 2 ligand (dmgH is dimethylglyoximate) in the equatorial plane and one Cl À anion and one N atom of ethyl nicotinate in apical positions, displays an approximately octahedral coordination. The Co atom is 0.0187 (8) Å out of the mean plane of the four equatorial N atoms. The structure has an OÁ Á ÁHÁ Á ÁO bridge, which is very common in cobaloxime derivatives, with OÁ Á ÁH distances of 1.24 (2) and 1.25 (2) Å .

Experimental
Crystal data [Co(C 4 (Schrayzer, 1968). Recently they have been also used to catalyze the proton reduction as a function model of hydrogenase (Razavet et al., 2005). The cobalt atom in the title compound, [Co(dmgH) 2 (3-(COOEt)C 5 H 4 N)Cl], is in a distorted octahedral geometry by four nitrogen atoms of the pseudomacrocyclic (dmgH) 2 ligand in the equatorial plane and by one chlorine atom and a nitrogen atom of ethyl nicotinate, respectively, in mutually trans positions (N5-Co-Cl1 = 179.88° (5)). The mean Co-N bond length is 1.8944 Å (16).

Experimental
Co(dmgH)(dmgH 2 )Cl, (3.6 g, 0.01 mol) and ethyl nicotinate (3.0 g, 0.02 mol) were added to chloroform (90 ml). The suspension was stirred for 20 minutes. Water (30 ml) was then added to the flask and the mixture was vigorously stirred for 2 h. The aqueous layer was discarded and the chloroform layer filtered and extracted with water until the washings were nearly colorless. The solution was reduced in volume and the product precipitated by addition of ethanol (95%); yield 69%.

Refinement
H1 and H2 were located from the difference Fourier map and there positions were refined freely. Other hydrogen atoms were placed in calculated positions and refined as riding with C-H = 0.93 Å (CH) and 0.97 Å (CH 3 ). The isotropic atomic displacement parameters of the the protons were constrained as follows: U iso (H) = 1.5U eq (C) for the methyl group and   Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.
Crystal data [Co(C 4

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 > σ(F 2 ) is used only for calculating Rfactors(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.