Diaquabis{4-[(pyridin-2-yl)methylideneamino]benzenesulfonato-κ2 N,N′}nickel(II) tetrahydrate

In the title complex, [Ni(C12H9N2O3S)2(H2O)2]·4H2O, the NiII ion is coordinated by four N atoms from two bidentate chelating 4-[(pyridin-2-yl)methylideneamino]benzenesulfonate ligands and two O atoms from cis-related water molecules in a slightly distorted octahedral environment [Ni—N = 2.071 (3)–2.121 (3) Å and Ni—O = 2.071 (2) and 2.073 (3) Å]. In the crystal, the coordinated water molecules and the four water molecules of solvation are involved in intermolecular O—H⋯O hydrogen-bonding interactions with water and sulfonate O-atom acceptors, giving a three-dimensional framework structure.

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL. The design and control of supramolecular coordination complex networks in which both coordinate bonds and hydrogen bonds take part in the molecular self-assenbly, have recently attracted increasing interest. Schiff base complexes that contain both sulfur and amino acid functionalities have also received much attention due to their potential application in pharmacy Zhang et al., 2007Zhang et al., , 2008. We report here the synthesis and the stucture of the mononuclear Ni II complex with the potentially tridentate monoanionic ligand from the acid (4-pyridylmethylimine)benzenesulfonic acid (BfbaH), the title complex [Ni (C 12 (Correia et al., 2003;Li et al., 2006;Huang et al., 2009;Ou-Yang et al., 2008).
The asymmetric unit of the title complex ( Fig. 1) comprises a Ni 2+ cation, coordinated by four N atoms from two bidentate Bfba ligands and two O atoms from cis-related water molecules in a slightly distorted octahedral environment  (Table 1) giving a three-dimensional framework structure (Fig. 2).

Experimental
The potassium salt of (4-pyridylmethylimine)benzenesulfonic acid (BfbaK) was synthesized according to the literature method (Casella & Gullotti, 1981). To prepare the title complex, the ligand BfbaK (1 mmol) was dissolved in methanol (10 ml) at 333 K and an aqueous solution (10 ml) containing Ni(AcO) 2 . 4H 2 O (0.5 mmol) was added. The resulting solution was stirred at 333 K for 4 h, then cooled to room temperature and filtered. Blue crystals of the title complex suitable for X-ray diffraction were obtained by slow evaporation of this solution over a period of several days (yield 50%).

Refinement
All H-atoms were placed in calculated positions with O-H = 0.85-0.87 Å and C-H = 0.93 Å and were allowed to ride in the refinement, with U</> iso (H) = 1.2U eq (C) or 1.5U eq (O).

Figure 1
The molecular structure of the title complex, showing the atom-numbering scheme. All H atoms have been omitted for clarity.

Figure 2
The packing of the title complex, showing the two-dimensional sheet structure in the ac plane.