catena-Poly[[(1,10-phenanthroline)cadmium(II)]-μ-2-(1,3-benzimidazol-2-ylsulfanyl)acetato-κ3 N 1,O:N 3]

In title compound, [Cd(C9H6N2O2S)(C12H8N2)]n, the CdII atom is in a distorted tetragonal-pyramidal environment, coordinated by one chelating 1,10-phenanthroline ligand, one chelating 2-(1,3-benzimidazol-2-ylsulfanyl)acetate (bia) ligand bound through one N atom and one O atom of the carboxyl group, and one N atom from a second bia ligand. Each bia ligand acts as bridge between CdII ions, forming one-dimensional coordination polymers along [010], with a shortest Cd⋯Cd distance of 4.27 (2) Å.

In title compound, [Cd(C 9 H 6 N 2 O 2 S)(C 12 H 8 N 2 )] n , the Cd II atom is in a distorted tetragonal-pyramidal environment, coordinated by one chelating 1,10-phenanthroline ligand, one chelating 2-(1,3-benzimidazol-2-ylsulfanyl)acetate (bia) ligand bound through one N atom and one O atom of the carboxyl group, and one N atom from a second bia ligand. Each bia ligand acts as bridge between Cd II ions, forming onedimensional coordination polymers along [010], with a shortest CdÁ Á ÁCd distance of 4.27 (2) Å .

S1. Comment
Recently, there has been significant interest in the rational design and synthesis of metal-organic coordination architectures by using flexible bridging units because the flexibility and conformational freedom of such ligands offers the possibility for construction of unprecedented frameworks (Zhang et al. 2008). Benzimidazole and thioether carboxylates have been widely used to construct many novel and interesting metal-organic frameworks. However, such metalorganic frameworks formed by bifunctional ligands including benzimidazole and thioether carboxylate have been rarely reported (Matthews et al. 1998). Herein, we report a new bifunctional flexible ligand 2-(1H-benzo[d]imidazol-2-ylthio)acetic acid (H 2 bia), and present the synthesis and structural characterization of a one-dimensional coordination polymer {Cd(bia)(phen)}n (phen = 1,10-phenanthroline).
The asymmetric unit of the title compound, contains a Cd II cation, a bia and a chelating phen. Each Cd II displays a distorted tetragonal pyramidal geometry, being surrounded by one phen ligand, one chelating bia and a N atom of another bia ligand. Each bia ligand acts as a bridge between two Cd II ions, forming one-dimensional coordination polymers along the b axis (Fig. 1). The shortest Cd···Cd distance in the chain is 4.27 (2) Å.

S2. Experimental
A mixture of H 2 bia (0.0208 g, 0.1 mmol), phen (0.0180 g, 0.1 mmol), Cd(NO 3 ) 2 .6H 2 O (0.0345 g, 0.1 mmol) and H 2 O (8 ml) was heated in a 15 ml Teflon-lined autoclave at 433 K for 3 days, followed by slow cooling (5 K h -1 ) to room temperature. The resulting mixture was washed with water, and colourless block crystals were collected and dried in air.

S3. Refinement
H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 or 0.97 Å and with U iso (H) = 1.2U eq (C).  The one-dimensional chain of the title compound. Displacement ellipsoids are shown at 50% probability and H atoms are omitted for clarity.

Crystal data
[Cd(C 9 H 6 N 2 O 2 S)(C 12 H 8 N 2 )] M r = 498.84 Monoclinic, P2 1 /c Hall symbol: -P 2ybc a = 9.2195 (10) Å b = 8.2577 (9)   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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq  (5)