catena-Poly[(diaquacadmium)-μ-4,4′-[sulfonylbis(1,4-phenyleneoxy)]diacetato-κ4 O,O′:O′′,O′′′]

In the title coordination polymer, [Cd(C16H12O8S)(H2O)2]n, the CdII ion is situated on a crystallographic twofold rotation axis, being coordinated by four O atoms from two bidentate 4,4′-[sulfonylbis(1,4-phenyleneoxy)]diacetate (L) ligands and two water molecules in a highly distorted CdO6 octahedral geometry. Each complete ligand L, which is also generated by twofold symmetry with the S atom lying on the rotation axis, bridges two CdII atoms to form a polymeric zigzag chain propagating in the [10-1] direction. O—H⋯O hydrogen bonds between the coordinated water molecules and carboxylate O atoms are involved in the packing.

In the title coordination polymer, [Cd(C 16 H 12 O 8 S)(H 2 O) 2 ] n , the Cd II ion is situated on a crystallographic twofold rotation axis, being coordinated by four O atoms from two bidentate 4,4 0 -[sulfonylbis(1,4-phenyleneoxy)]diacetate (L) ligands and two water molecules in a highly distorted CdO 6 octahedral geometry. Each complete ligand L, which is also generated by twofold symmetry with the S atom lying on the rotation axis, bridges two Cd II atoms to form a polymeric zigzag chain propagating in the [101] direction. O-HÁ Á ÁO hydrogen bonds between the coordinated water molecules and carboxylate O atoms are involved in the packing.

Zhan-Ling Ma Comment
A large family of coordination polymers has been developed recently owing to their potential applications as functional solid materials and their intriguing architectures or topologies. In the past ten years, there has been a growing interest in metal-organic frameworks involving semi-rigid V-shaped dicarboxylate ligands (Tanaka et al., 2008;Zheng et al., 2009Zheng et al., , 2010. 4,4′-sulfonyldi-p-phenylenedioxydiacetic acid is a typical example of a semi-rigid V-shaped dicarboxylate ligand. To the best of our knowledge, there has been no report about its coordination compounds. Recently, we obtained the title cadium polymer (I), its crystal structure is reported here.
In the structure of (I) each cadium(II) atom is coordinated by four oxygen atoms from two 4,4′-sulfonyldi-p-phenylenedioxydiacetate ligands and two water molecules, displays a highly distorted octahedral geometry (Fig. 1). Each ligand L bridges two cadium(II) centers to form polymeric zigzag chain propagated in direction [101] (Fig. 2). Moreover, there are Intermolecular O-H···O hydrogen bonds between the coordinated water molecules and the carboxylate O atoms consolidate the further crystal packing (Table 1).

Experimental
A mixture of Cd(Ac) 2 (0.5 mmol), 4,4′-sulfonyldi-p-phenylenedioxydiacetic acid (0.5 mmol), NaOH (1 mmol) and H 2 O (15 ml) was placed in a 23 ml Teflon reactor, which was heated at 413 K for three days and then cooled to room temperature. Colourless blocks were obtained on cooling, which were washed with water and dried in air.

Figure 2
The one-dimensional zigzag chain structure of the title compound.

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.