Crystal structure of cis-tetraaquadichloridocobalt(II) sulfolane disolvate

In the title compound, [CoCl2(H2O)4]·2C4H8SO2, the CoII cation is located on the twofold rotation axis and is coordinated by four water molecules and two adjacent chloride ligands in a slightly distorted octahedral coordination environment. The cisoid angles are in the range 83.27 (5)–99.66 (2)°. The three transoid angles deviate significantly from the ideal linear angle. The crystal packing can be described as a linear arrangement of complex units along c formed by bifurcated O—H⋯Cl hydrogen bonds between two water molecules from one complex unit towards one chloride ligand of the neighbouring complex. Two solvent molecules per complex are attached to this infinite chain via O—H⋯O hydrogen bonds in which water molecules act as the hydrogen-bond donor and sulfolane O atoms as the hydrogen-bond acceptor sites.

The structure of the compound consists of discrete tetraaquadichlorocobalt(II) complexes stacked in chains parallel to the c axis. The Co II cation is coordinated by four water molecules and two adjacent chloride ligands in a slightly distorted octahedral geometry. The two Co-Cl distances are 2.510 (6) Å and the Co-O distances are between 2.165 (3) and 2.243 (3) Å in good agreement with that found in mineral compound CoCl 2 O 4 H 8 (Waizumi et al., 1990)

S2. Experimental
A solution of CoCl 2 × 2 H 2 O (34 mg, 0.2 mmol) in water (10 ml) was added dropwise to a solution of sulfolane (24 mg, 0.2 mmol) in water (10 ml). The mixture was then refluxed with stirring for 3 h and the resulting solution was left to stand at room temperature. After several days, blue crystals were obtained and dried under vacuum (yield: 55%).

S3. Refinement
All non-H atoms were refined with anisotropic displacement parameters. Approximate positions for all H atoms were first obtained from the difference electron density map. However, the H atoms were situated into idealized positions and the H-atoms have been refined within the riding atom approximation with C-H = 0.93 Å and U iso = 1.2U eq (C) except for H atoms of water molecules, which were refined isotropically using the following restraints: O-H = 0.84 (2) Å, H···H = 1.45 (2) Å and U iso = 1.5U eq (O).

Figure 1
Molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level. Only the asymmetric unit is labelled. H atoms are represented as small spheres of arbitrary radii.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.