catena-Poly[[diaquabis(3-methylpyridine-κN)cobalt(II)]-μ-sulfato-κ2 O:O′]

The environment of the CoII ion in the title compound, [Co(SO4)(C6H7N)2(H2O)2]n, exhibits an octahedral configuration with the two 3-methylpyridine ligands lying in cis positions with respect to each other and trans to the two coordinated water molecules. The axial positions are occupied by O atoms of the sulfate ions. Co and S atoms occupy special positions (twofold axis, Wyckoff position 4c). Neighboring CoII ions are covalently connected with each other through the sulfate ions, thus creating infinite polymeric chains that run along the c axis. The water molecules are connected with neighboring sulfate ions through strong O—H⋯O hydrogen bonds. Intramolecular hydrogen bonds parallel to the propagation direction of the chains stabilize the polymeric chains, and intermolecular hydrogen bonds between chains connect neighboring chains with each other, thus leading to polymeric double chains.

The environment of the Co II ion in the title compound, [Co(SO 4 )(C 6 H 7 N) 2 (H 2 O) 2 ] n , exhibits an octahedral configuration with the two 3-methylpyridine ligands lying in cis positions with respect to each other and trans to the two coordinated water molecules. The axial positions are occupied by O atoms of the sulfate ions. Co and S atoms occupy special positions (twofold axis, Wyckoff position 4c). Neighboring Co II ions are covalently connected with each other through the sulfate ions, thus creating infinite polymeric chains that run along the c axis. The water molecules are connected with neighboring sulfate ions through strong O-HÁ Á ÁO hydrogen bonds. Intramolecular hydrogen bonds parallel to the propagation direction of the chains stabilize the polymeric chains, and intermolecular hydrogen bonds between chains connect neighboring chains with each other, thus leading to polymeric double chains.

Comment
Sulfate coordination to cobalt ions may be divided into three commonly reported modes: monodentate (Das et al.,2009, Majumder et al., 2005, bidentate (Masuhara et al.., 2007, Zhong et al.,2006, 2011 or bidentate-bridged metal to metal coordination (Dietz et al., 2009, Wu et al., 2008, Carlucci et al., 2003, Ali et al., 2005, Vreshch et al., 2003. The last mode of coordination is particularly common where the sulfate ion acts as a bridge that links two cobalt ions to form an extended polymeric structure. Further evidence for the different modes of sulfate coordination is reflected in the infra-red absorption spectrum due to the reduction in symmetry in sulfate coordination. In the title compound, the cobalt(II) complex exhibits octahedral symmetry with the two 3-methylpyridine ligands lying in

Experimental
Potassium O-n-butyl xanthate (1.00 g, 0.53 mmol) was dissolved in acetone (20 mL) and placed in a three-necked round bottom flask fitted with a reflux condenser, a magnetic stirrer and a vacuum line. Co(NO 3 ) 2 .6H 2 O (0.78 g, 2.70 mmol) was added directly into the reaction flask. The contents were stirred to dissolve the salt completely. About 30 ml of 3-methylpyridine was added and stirring was continued for another hour. Any insoluble matter was removed by filtration, and slow evaporation of the reaction mixture at room temperature yielded 60% of red needles of the title compound as the unexpected product. m.p. = 373 K. Elemental analysis: Found (Calc.) for C 12 H 18 N 2 CoO 6 S: C 38.64 (38.20); H 4.66 (4.80); N 7.51 (7.42).

Refinement
Water hydrogen atoms were located in the difference density Fourier map and their position were refined with an O-H distance restraint of 0.84 Å within a standard deviation of 0.02 Å. All other hydrogen atoms were placed in calculated positions and all H atoms were refined riding on the respective carrier atom with an isotropic displacement parameter 1.5 (methyl, hydroxyl) or 1.2 times (aromatic) that of the adjacent carbon or oxygen atom.

catena-Poly[[diaquabis(3-methylpyridine-κN)cobalt(II)]-µ-sulfato-κ 2 O:O']
Crystal data [Co(SO 4  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.