catena-Poly[[(2-methylbenzoato-κ2 O,O′)sodium]-di-μ-aqua-κ4 O:O′]

In the title coordination polymer, [Na(C8H7O2)(H2O)2]n, the cation is chelated by the carboxylate O atoms of the anion in a bidentate mode and is surrounded by the O atoms of four water molecules. The coordination of the Na+ cation is distorted octahedral. The water molecules bridge adjacent metal cations, forming polymeric layers parallel to (100). The structure is stabilized by an extensive network of O—H⋯O hydrogen bonds.

In the title coordination polymer, [Na(C 8 H 7 O 2 )(H 2 O) 2 ] n , the cation is chelated by the carboxylate O atoms of the anion in a bidentate mode and is surrounded by the O atoms of four water molecules. The coordination of the Na + cation is distorted octahedral. The water molecules bridge adjacent metal cations, forming polymeric layers parallel to (100). The structure is stabilized by an extensive network of O-HÁ Á ÁO hydrogen bonds.

Related literature
Tin complexes with organic ligands have been studied intensively due to their biological activity, see, for example: Shahzadi et al. (2007). For 2-methylbenzoic and 4-methylbenzoic acids as potent allergic sensitizers when applied to human skin, see: Emmet & Suskind (1973), and as inhibitors of lettuce fruit germination, see: Reynolds (1978). Sodium 2-methylbenzoate has been studied as a precursor in the synthesis of biologically active tin(IV) complexes. For the structure of a sodium complex with a 2-methyl-3,5-dinitrobenzoate ligand, see: Danish et al. (2010).
In the polymeric structure of the title compound, [Na(C 8 H 7 O 2 )(H 2 O) 2 ] n , each sodium ion is coordinated by the carboxylic O atoms of the bidentate anion and by four bridging water O atoms (Fig.1). The coordination geometry around the Na + cation is distorted octahedral with the equatorial plane composed of the carboxylate atoms O1 and O2 and the symmetryrelated water O4 and O4 i atoms [r.m.s. is 0.0580 (2) Å]. Water O3 and O3 ii atoms are at the apical positions. The resulting coordination differs from the one reported in the structure of the Na + complex with the 2-methyl-3,5-dinitrobenzoate anion.
Here the metal exhibits coordination number 7 (Danish et al., 2010). The 2-methylbenzoate ring in the title compound is planar with a r.m.s. of 0.0089 (2) Å; the carboxylic group C17/O1/O2 makes an dihedral angle of 37.1 (2)° with the aromatic ring. Na + cations form sheets parallel to the (100) plane in which they are grouped into pairs (Fig. 2). In such a pair, Na + cations are coordinated by ligands with their 2-methylbenzoate rings pointing in the same direction but twisted by an angle  Table 2.
Experimental 50 ml of an aqueous solution containing 0.0147 mmol of 2-methylbenzoic acid were added dropwise with continuous stirring at room trmperature to 50 ml of an aqueous solution of sodium bicarbonate (0.0147 mmol). The mixture was then refluxed for 3 hours, cooled to room temperature and concentrated under reduced pressure to afford a dry solid mass which was then purified by re-crystallization from a distilled water-ethanol (4:1) mixture to obtain single crystals.

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