Poly[μ5-(4-methoxybenzenesulfonato)-sodium]

In the title complex, [Na(C7H7O4S)]n, the NaI ion is coordinated in a slightly distorted pentagonal-bipyramidal environment by seven O atoms [Na—O = 2.3198 (16)–2.5585 (17) Å]. The 4-methoxybenzenesulfonate anions act as bis-chelating and bridging ligands, forming a two-dimensional polymer parallel to (001), which is further linked into a three-dimensional network by weak C—H⋯O hydrogen bonds.

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL, PLATON (Spek, 2009), Mercury and publCIF (Westrip, 2010 Aromatic sulfonic acids are one of several useful sulfonic acids which are frequently used as chemical reagents (King, 1991) such as reagents for phenol preparation. They are also widely used as acid catalysts in organic reactions (Siril et al., 2007) such as for the deprotection of O-allylphenols (Babu et al., 2003). Salts of benzenesulfonic acid exhibit pharmaceutical and biological activities (Chanawanno et al., 2010;Taylor et al., 2006), and are also used for nonlinear optical material preparations (Ruanwas et al., 2010) and as raw materials in detergent manufacture (Schöngut et al., 2011). Based on these significant roles played by aromatic sulfonic acids, we have synthesized the sodium salt of 4-methoxybenzenesulfonate and herein we report the crystal structure of the title compound (I).
Within the title coordination polymer there are tetranuclear clusters containing four Na I ions and four 4-methoxybenzenesulfonate ligands (Fig. 1). All three O atoms of the 4-methoxybenzenesulfonate ligands are involved in coordination to the Na I ion. The coordination modes of the sulfonate unit are chelating bidentate and bridging monodentate linking two Na I ions. Each Na I is in a distorted pentagonal-bipyramidal geometry ( Fig. 2) with three pairs of chelating O atoms from the three bidentate sulfonate groups and one bridging O atom from another monodentate sulfonate group which is also coordinated to a symmetry related Na I ion. The distance of the Na I ion from the mean plane of the O 5 equatorial atoms is 0.127 Å. Bond lengths (Allen et al., 1987) and angles in the ligand are in normal ranges. The Na-O bond distances in the equatorial plane range from 2.3198 (16) -2.5585 (17) Å, and the two axial Na-O bond distances are 2.3734 (17) and 2.4637 (16) Å. The O-Na-O bond angles in the equatorial plane are in the range 56.76 (5)-85.88 (6) ° and the axial angle is 158.12 (7)°. These values are comparable to those reported for another Na-O donor complex (Smith et al., 2004). The overall structure is a two-dimensional polymer parallel to (001) (Fig. 3). In addition, weak C-H···O hydrogen bonds (Table 1) link the polymer into a three-dimensional network (Fig. 4).

Experimental
To a solution of 4-methoxybenzenesulfonyl chloride (3.00 g, 14.50 mmol) in hot methanol, sodium hydroxide (0.58 g, 14.50 mmol) was added. The suspension was stirred for 1 h. The reaction mixture was then cooled to the room temperature and the resulting white solid formed was filtered off and washed with CH 3 OH. Colorless needle-shaped single crystals suitable for X-ray structure determination were recrystallized from a solution of (I) in CH 3 OH by slow evaporation at room temperature over a few days.

Refinement
All H atoms were fixed geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and 0.96 for CH 3 . The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.

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.