catena-Poly[[[diiodidocadmium(II)]-μ-1-(4-pyridylmethyl)-1H-benzimidazole] methanol hemisolvate]

In the title coordination polymer, {[CdI2(C13H11N3)]·0.5CH4O}n, each CdII center is four-coordinated by two N-atom donors from two 1-(4-pyridylmethyl)-1H-benzimidazole (L) ligands and two iodide anions, forming a tetrahedral coordination geometry. L ligands bridge adjacent CdII ions, generating two crystallographically independent approximately orthogonal one-dimensional chains. The methanol solvent molecule associates with one of the chains via O—H⋯I interactions.

In the title coordination polymer, {[CdI 2 (C 13 H 11 N 3 )]Á0.5-0.5CH 4 O} n , each Cd II center is four-coordinated by two Natom donors from two 1-(4-pyridylmethyl)-1H-benzimidazole (L) ligands and two iodide anions, forming a tetrahedral coordination geometry. L ligands bridge adjacent Cd II ions, generating two crystallographically independent approximately orthogonal one-dimensional chains. The methanol solvent molecule associates with one of the chains via O-HÁ Á ÁI interactions.

Related literature
For a review of N-containing heterocyclic aromatic compounds as bridging ligands, see: Steel (2005). For a discussion of benzimidazole ligands in complexes, see: Li et al. (2007); Meng et al. (2004). For an example of a silver coordination polymer of the present ligand, see: Huang et al. (2006). For bond-length data, see: Allen et al. (1987).

catena-Poly[[[diiodidocadmium(II)]-µ-1-(4-pyridylmethyl)-1H-benzimidazole]
methanol hemisolvate] Jun-Jie Wang, Li-Fan Yan and Tong-Liang Hu S1. Comment N-containing heterocyclic aromatic compounds are extensively used as bridging ligands in coordination and metallosupramolecular chemistry (Steel, 2005). In recent years, benzimidazole groups have been used to link different alkyl or aromatic groups to form a series of bi-and multi-dentate flexible ligands, which can adopt different conformations according to the different geometric requirements of the metal centers when forming complexes (Li et al., 2007). Many complexes with these ligands show unique structural topologies and interesting properties (Meng et al., 2004). Recently, Liu and co-workers synthesized a flexible bridging ligand 1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazole (L) as well as its chiral one-dimensional double helix polymer, [Ag(L)(NO 3 )] n (Huang et al., 2006). We herein report the crystal structure of a cadmium complex of this ligand (I).
In the molecule of (I), ( Fig. 1 and 2), the bond lengths and angles (Table 1) are generally within normal ranges (Allen et al., 1987). The Cd II center is tetrahedrally coordinated by two N atoms from two L ligands (L = 1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazole) and two iodide ions. In the extended structure of (I), the Cd II centers are interconnected by L ligands to form two one-dimensional chains along two different directions (Fig. 3). The chain containing Cd1 is along the c direction and the other one containing Cd2 is along the b direction, making them essentially orthogonal. The methanol solvate molecules are associated with the Cd1 chains via O-H···I interactions.

S2. Experimental
The ligand 1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazole (L) was synthesized according to a reported method (Li et al., 2007). The reaction of L (58 mg, 0.2 mmol), NaI (30 mg, 0.2 mmol) and Cd(ClO 4 ) 2 (31 mg, 0.1 mmol) in a solution of methanol and water (v/v = 1:1,10 ml) for a few minutes afforded a white solid, which was separated by filtration. The resulting solution was kept at room temperature. Colorless single crystals suitable for X-ray analysis were obtained by slow evaporation of the solvent after several days (yield: 40%).

S3. Refinement
H atoms were included in calculated positions and treated in the subsequent refinement as riding atoms, with C-H = 0.93 (aromatic) and 0.97 Å (methylene) and U iso (H) = 1.2*U eq (C).    View of the two crystallographically independent one-dimensional chains that run along the b and c axes.

catena-Poly[[[diiodidocadmium(II)]-µ-1-(4-pyridylmethyl)-1H-benzimidazole] methanol hemisolvate]
Crystal data 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)