catena-Poly[(diaquastrontium)-bis(μ-2-methyl-3,5-dinitrobenzoato)]

The title compound, [Sr(C8H5N2O6)2(H2O)2]n, essentially consists of a one-dimensional polymeric network with Sr2O2 rings extending along the [100] direction. The range of Sr—O bond lengths is 2.4822 (13)–2.8113 (13) Å. C—H⋯O and O—H⋯O hydrogen-bonding interactions stabilize the molecules in the form of a two-dimensional polymeric network parallel to (001). One of the nitro groups is disordered over three sets of sites with the occupancy ratio of 0.46:0.32:0.22.

The title compound, [Sr(C 8 H 5 N 2 O 6 ) 2 (H 2 O) 2 ] n , essentially consists of a one-dimensional polymeric network with Sr 2 O 2 rings extending along the [100] direction. The range of Sr-O bond lengths is 2.4822 (13)-2.8113 (13) Å . C-HÁ Á ÁO and O-HÁ Á ÁO hydrogen-bonding interactions stabilize the molecules in the form of a two-dimensional polymeric network parallel to (001). One of the nitro groups is disordered over three sets of sites with the occupancy ratio of 0.46:0.32:0.22.
In the title compound, the Sr +2 cation is coordinated to eight O-atoms. Six O-atoms are of four carboxylate groups and two O-atoms from two water molecules. Each ligand of 2-methyl-3,5-dinitrobenzoic acid is chelated and bridged from a The molecules are stabilized in the form of two-dimensional polymeric network along the plane (001) due to intra as well as inter-molecular H-bondings of C-H···O and O-H···O types (Table 1).

Experimental
Anhydrous strontium chloride (1.585 g, 0.01 mol) of was dissolved in 25 ml distilled water in 100 ml round bottom flask. Sodium salt of 3,5-dinitro-ortho-toluic acid (4.96 g, 0.02 mol) was dissolved in 15 ml of distilled water and added to the strontium chloride solution drop-wise. After complete addition, the reaction mixture was refluxed for 3 h. The reaction mixture was cooled to room temperature and given activated charcoal treatment and filtered. The filtrate was concentrated and kept for crystallization. Light brown prisms appeared within one week.
Decomposition point was 620 K.

supplementary materials sup-2 Refinement
The O-atoms of one nitro group are fully disordered over three set of sites with occupancy ratio of 0.46:0.32:0.22. The occupancy factors were initially refined restraining their sum to be equal to 1. Then, once stabilized, they were fixed.
The coordiantes of these disordered O atoms were refined using restraints (similar distance for all N-O bonds) and their anisotropic thermal displacement parameters were restrained to be all equal.
All H atoms attached to C atoms and N atom were fixed geometrically and treated as riding with (C-H = 0.93-0.96 Å) with U iso (H) = xU eq (C), where x = 1.5 for methyl and x = 1.2 for aromatic H-atoms. H atoms of water molecule were located in difference Fourier maps and included in the subsequent refinement using restraints (O-H= 0.85 (1)Å and H···H= 1.40 (2)Å) with U iso (H) = 1.5U eq (O). In the last cycles of refinement, they were considered as riding on their parent O atoms.
Crystal data [Sr(C 8

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (