Diaquabis(dimethyl sulfoxide-κO)bis(saccharinato-κN)cobalt(II)

The title complex, [Co(C7H4NO3S)2(C2H6OS)2(H2O)2], contains a Co2+ cation in an octahedral coordination environment. The metal atom is surrounded by two different neutral ligands, namely dimethylsulfoxide (DMSO) and water, each coordinating through the O atom. The anionic saccharinate (sac; 1,1,3-trioxo-2,3-dihydro-1λ6,2-benzothiazol-2-ide) ligand coordinates through the N atom. Each of the three similar ligand pairs is in a trans configuration with respect to each other. The Co atom lies on a crystallographic center of symmetry and the octahedral geometry is not significantly distorted. A short O—H⋯O hydrogen bond is present between a water H atom and the ketone O atom; two longer hydrogen bonds (intra- and intermolecular) are also present between a water H and a sulfonic O atom, forming a supramolecular assembly through head-to-tail aggregation between adjacent complexes.

The title complex, [Co(C 7 H 4 NO 3 S) 2 (C 2 H 6 OS) 2 (H 2 O) 2 ], contains a Co 2+ cation in an octahedral coordination environment. The metal atom is surrounded by two different neutral ligands, namely dimethylsulfoxide (DMSO) and water, each coordinating through the O atom. The anionic saccharinate (sac; 1,1,3-trioxo-2,3-dihydro-1 6 ,2-benzothiazol-2-ide) ligand coordinates through the N atom. Each of the three similar ligand pairs is in a trans configuration with respect to each other. The Co atom lies on a crystallographic center of symmetry and the octahedral geometry is not significantly distorted. A short O-HÁ Á ÁO hydrogen bond is present between a water H atom and the ketone O atom; two longer hydrogen bonds (intra-and intermolecular) are also present between a water H and a sulfonic O atom, forming a supramolecular assembly through head-to-tail aggregation between adjacent complexes.

Related literature
For a general review article on the coordination chemistry of saccharinate ligands, see: Baran & Yilmaz (2006). For cobalt(II) saccharinate complexes, see: Deng et al. (2008) and for cobalt(II) complexes with saccharinate as a non-coordinating ligand, see: Batsanov et al. (2011). For the preparation of cobalt(II) and other divalent metal precursor complexes, see : Haider et al. (1985).
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; 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: SHELXL97. plexes. In cases where the incoming neutral ligand is relatively bulky, as in the present study, it causes steric hindrance and only two of the four aqua ligands become displaced in order for the Co center to remain octahedral. Although there are a number of Co(II) saccharinate complexes previously reported (Batsanov et al., 2011, and refs. therein), the present study reports the first example of a structurally characterized Co(II) complex that contains both saccharinate and dmso ligands.

Experimental
[Co(sac) 2 (H 2 O) 4 ].2H 2 O was prepared as per literature method (Haider et al., 1985). The red crystals of [Co(sac) 2 (H 2 O) 4 ].2H 2 O (0.932 g; 1.80 mmol) was placed in a 100 ml beaker and dissolved in excess amount of dimethyl sulfoxide (dmso) (20 ml). The reaction mixture was gently heated on a heating plate with stirring to reduce the volume of dmso to ~7 ml. The beaker was removed from the heat source and allowed to stand for 10 days during which time large light red blocky crystals of the title compound were obtained. Yield (1.00 g, 93.0%). Mp: 393 K; 120 ° C. IR-ATR (cm -1 ): 3486.98, 3005.41 n(OH); 1618 n(C=O); 1584, 1460 n(C=C); 1256 n(O=S=O); 1141, 949 n(S=O). No NMR data were recorded due to the paramagnetic nature of the Co(II) complex. Single crystals were obtained by slow evaporation of dmso solvent.

Refinement
All hydrogen atoms could be found in the difference electron density maps. All, except H5A and H5B on O5, were placed in idealised positions refining in riding models with Uiso set at 1.2 or 1.5 times those of their parent atoms. The water hydrogen atoms H5A and H5B were located in the difference electron density maps and refined with independent isotropic  Fig. 1. The ORTEP molecular structure of the title complex, shown with 50% probability ellipsoids.