Hexaaquacadmium(II) bis[4-(2-hydroxybenzylideneamino)benzenesulfonate] dihydrate

In the title compound, [Cd(H2O)6](C13H10NO4S)2·2H2O, the Cd atom (site symmetry ) adopts a regular octahedral coordination and the anion is stabilized by an intramolecular O—H⋯N hydrogen bond. O—H⋯O hydrogen bonds involving the coordinated and uncoordinated water molecules lead to a three-dimensional network.

In the title compound, [Cd(H 2 O) 6 ](C 13 H 10 NO 4 S) 2 Á2H 2 O, the Cd atom (site symmetry 1) adopts a regular octahedral coordination and the anion is stabilized by an intramolecular O-HÁ Á ÁN hydrogen bond. O-HÁ Á ÁO hydrogen bonds involving the coordinated and uncoordinated water molecules lead to a three-dimensional network.

Related literature
For related literature, see: Tai et al. (2008).
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. As part of our ongoing studies of the synthesis and coordination chemistry of Schiff-base ligands (e.g. Tai et al., 2008), we now report the synthesis and structure of the title compound, (I), (Fig. 1), in which the organic species does not coordiate to the metal and a hydrated molecular salt arises.
The Cd atom (site symmetry 1) in (I) is bonded to six water molecules ( Table 1). The anion is stablisied by an intramolecular O-H···N hydrogen bond (Table 2), which perhaps correlates with the fact that the aromatic rings are almost co-planar [dihedral angle = 4.09 (14)°].
The water molecules, both bound and unbound, participate in O-H···O hydrogen bonds to link the component speices into a three-dimensional network.

S2. Experimental
1 mmol of cadmium nitrate was added to a solution of salicylaldehyde-4-aminobenzene sulfonic acid (1 mmol) in 10 ml of 95% ethanol. The mixture was stirred for 2 h at refluxing temperature. Evaporating some ethanol, clear blocks of (I) were obtained after one weeks.

Hexaaquacadmium(II) bis[4-(2-hydroxybenzylideneamino)benzenesulfonate] dihydrate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.60 e Å −3 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.