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

In the title polymeric complex, [Ni(C2H6NO3S)2]n, the NiII ion occupies a special position on an inversion centre and displays a slightly distorted octahedral coordination geometry, being linked to four sulfonate O atoms and to two N atoms of the taurine ligands. The sulfonate groups doubly bridge symmetry-related NiII centers, forming polymeric chains along the a axis.

In the title polymeric complex, [Ni(C 2 H 6 NO 3 S) 2 ] n , the Ni II ion occupies a special position on an inversion centre and displays a slightly distorted octahedral coordination geometry, being linked to four sulfonate O atoms and to two N atoms of the taurine ligands. The sulfonate groups doubly bridge symmetry-related Ni II centers, forming polymeric chains along the a axis.

Comment
Taurine, an amino acid containing sulfur, is indispensable to human beings because of its applications in medicine and biochemistry (Bottari & Festa, 1998;Zhang & Jiang, 2002;Zeng et al., 2003;Zhong et al., 2003). Several taurine complexes and their derivatives have recently been prepared in our laboratory (Cai et al., 2004;Jiang et al., 2005;Cai et al., 2006). As part of our ongoing investigation, the title polymeric Ni II complex, (I), has been prepared and its structure determined.
A segment of the polymeric structure of (I) is illustrated in Fig. 1. The Ni II ion is coordinated by four sulfonate O atoms and to two N atoms of the taurine ligands, displaying distorted octahedral coordination geometry. The sulfonate anions act as bridging ligands in (I). Neighbouring Ni atoms are bridged by two sulfonate anions, to form a zigzag polymeric chain along the a axis, as shown in Fig. 2. The polymeric chain has a repeat unit formed by two taurine and two Ni II atoms related by an inversion centre, which coincides with the centre of the eight-membered Ni 2 S 2 O 4 ring formed by the atoms of two bridging ligands and the Ni atoms; the distance between the two Ni atoms is 5.100 (12) 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 O3.

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 Ni(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 393 K for five days. Thereafter, the reactor was slowly cooled to room temperature and green block-shaped crystals suitable for X-ray diffraction were collected.

Refinement
H atoms were positioned geometrically (C-H = 0.97 Å and N-H = 0.80 Å) and included in the refinement in the ridingmodel approximation, with U iso (H) = 1.2U eq (carrier atom). Fig. 1. A segment of the polymeric structure of (I) with 30% probability displacement ellipsoids (arbitrary spheres for H atoms) supplementary materials sup-2