catena-Poly[cobalt(II)-bis(μ-2-aminoethanesulfonato)-κ3 N,O:O′;κ3 O:N,O′]

The hydrothermally prepared title compound, [Co(C2H6NO3S)2]n, is isotypic with its NiII analogue. The CoII cation is in a distorted octahedral environment, coordinated by four sulfonate O atoms and two N atoms from the taurine ligands. In comparison with the NiII analogue, the Co—N and Co—O bonds are longer than the Ni—N and Ni—O bonds, whereas all other bond lengths and angles as well as the hydrogen-bonding motifs are very similar in the two structures. The sulfonate groups doubly bridge symmetry-related CoII atoms, forming polymeric chains along the a axis. N—H⋯O hydrogen bonding interactions consolidate the crystal packing.


Comment
Taurine, an amino acid containing sulfur, is indispensable to human beings because of its important physiological functions (Bottari & Festa, 1998). Some metal complexes of the deprotonated sulfonic acid-type amino-acid taurine, C 2 H 6 NO 3 S -, have been reported (Cai et al., 2004;Jiang et al., 2005;Cai et al., 2006). As part of our investigations into novel structures of taurine complex, we have synthesized the title compound, a new Co II complex.
The coordinated modes of the title compound are similar to our previously reported Ni II structure (Yang et al., 2010).
As shown in Fig. 1, the Co II atom is coordinated by four sulfonate O atoms and to two N atoms of the taurine ligands, displaying a distorted octahedral coordination geometry. Neighbouring Co II atoms are bridged by two sulfonate anions to form zigzag polymeric chains along the a axis, as shown in Fig. 2. The polymeric chain has a repeat unit formed by two taurine ligands and two Co II atoms related by an inversion centre, which coincides with the centre of the eight-membered Co 2 S 2 O 4 ring. The shortest distance between two Co atoms is 5.139 (6) Å.
In the structure of the title compound there are two symmetry-independent 'active' H atoms; both of them belong to the NH 2 group of the taurine ligand. They form intramolecular hydrogen bonds with sulfonate atom O 3 .

Experimental
A solution of taurine (1.0 mmol) and KOH (1.0 mmol) in anhydrous methanol (10 ml) was added slowly to a solution of Co(CH 3 COO) 2 (1.0 mmol) in anhydrous methanol (10 ml). After stirring for 10 min, it was then dropped into a 25 ml Teflon-lined stainless steel reactor and heated at 383 K for six days. Thereafter, the reactor was slowly cooled to room temperature and pink block-shaped crystals suitable for X-ray diffraction were collected.

Refinement
The H atoms bound to C atoms were positioned geometrically with C-H = 0.97 Å and included in the refinement in the riding-model approximation with U iso (H) = 1.2U eq (C). The H atoms bound to N were located in a difference Fourier map and freely refined with U iso (H) = 1.2U eq (N).