fac-Tris(pyridine-2-carboxylato-κ2 N,O)cobalt(III)

In the title compound, [Co(C6H4NO2)3], the CoIII ion lies on a threefold rotation axis and is in a distorted octahedral environment defined by three N and three O donor atoms from three fac-disposed pyridine-2-carboxylate ligands. The ligands are coordinated in a chelate fashion, forming three five-membered rings. In the crystal, translationally related complex molecules are organized into columns along [001] via C—H⋯O hydrogen bonds.

In the title compound, [Co(C 6 H 4 NO 2 ) 3 ], the Co III ion lies on a threefold rotation axis and is in a distorted octahedral environment defined by three N and three O donor atoms from three fac-disposed pyridine-2-carboxylate ligands. The ligands are coordinated in a chelate fashion, forming three five-membered rings. In the crystal, translationally related complex molecules are organized into columns along [001] via C-HÁ Á ÁO hydrogen bonds.

fac-Tris(pyridine-2-carboxylato-
In the title compound, the Co III ion lies on a threefold rotation axis and is in a distorted octahedral environment of three N and three O donor atoms from three pyridine-2-carboxylate ligands (Fig. 1). Unlike in the case of earlier reported tris(pyridine-2-carboxylato)cobalt(III) monohydrate, in which the realization of mer-isomer is observed, in the title complex three pyridine-2-carboxylate ligands are disposed in a fac-fashion (Fu & Wang, 2005;Pelizzi & Pelizzi, 1981). The ligands are coordinated in a chelate mode, forming three five-membered rings. The Co-N and Co-O bond lengths are consistent with the values typically quoted for the octahedral cobalt(III) complexes with N,O-mixed donor ligands (Mokhir et al., 2002;Sliva et al., 1997). The C-O bond lengths in the deprotonated carboxylate groups of the ligands differ significantly [1.232 (14) and 1.339 (15) Å], which is typical for monodentately coordinated carboxylates (Wörl, Fritsky et al., 2005;Wörl, Pritzkow et al., 2005). The C-C and C-N bond lengths in the pyridine rings are normal for 2-substituted pyridine derivatives (Fritsky et al., 2001;Kovbasyuk et al., 2004;Krämer & Fritsky, 2000;Moroz et al., 2010).
In the crystal, the translational complex molecules are organized into columns along the c axis (Fig. 2). The neighboring molecules are united by C-H···O hydrogen bonds (Table 1).

Experimental
Cobalt(II) perchlorate hexahydrate (0.0365 g, 0.1 mmol) was dissolved in water (3 ml) and mixed with a solution of pyridine-2-hydroxamic acid (0.0414 g, 0.3 mmol) (Hynes, 1970) in methanol (3 ml). The resulting clear red solution was set aside for crystallization by slow diffusion of diethyl ether into the formed solution. The pink crystals formed in 5-7 days were filtered off, washed with diethyl ether and air-dried (yield: 83%).

Special details
Experimental. The final structural refinement was performed by using the twin law -1 -1 0 0 1 0 0 0 -1 with the final BASF parameter refining to 0.80178.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq