Crystal structure of catena-poly[1,3-dibenzylbenzimidazolium [[chloridomercurate(II)]-di-μ-chlorido]]

The asymmetric unit of the polymeric title compound, {(C21H19N2)[HgCl3]}n, comprises one-half of the cationic molecule, the other half being generated by application of twofold rotation symmetry, one Hg and two Cl atoms. The HgII atom, lying on a twofold rotation axis, exhibits a distorted triangular coordination environment and is surrounded by three Cl atoms with Hg—Cl distances in the range 2.359 (2)–2.4754 (13) Å. Two additional longer distances [Hg⋯Cl = 3.104 (14) Å] lead to the formation of polymeric [HgCl1/1Cl4/2]− chains extending along [001]. The crystal packing can be described by cationic layers alternating parallel to (-110) with the anionic chains located between the layers. The packing is consolidated by π–π stacking interactions between the benzene rings of the central benzimidazole entities, with centroid-to-centroid distances of 3.643 (3) Å.


Related literature
Benzimidazoles and their derivatives show anti-oxidant (Kuş et al., 2004), antifungal (Preston, 1974) and anthelminthic (Hazelton et al., 1995) properties and have applications in pharmacy and agriculture (Malek et al., 2006). They can also be used as epoxy resin curing agents, catalysts, metallic surface treatment agents (Li et al., 2003;Abboud et al., 2006) or as ionic liquids (Li et al., 2011;Chen et al., 2008). For the importance of transition metals ions in biological processes, see: Kaim & Schwederski (1994). For bond lengths of delocalized systems, see: Ennajih et al. (2009 Mebarek Bahnous S1. Experimental 1,3-Dibenzylbenzimidazolium trichloridomercurate(II) was synthesized by reaction of 1 mmol of 1,3-dibenzylbenzimidazolium chloride with 1 mmol of mercury(II) chloride in methanol at room temperature. The solid obtained was recrystallized in methanol to yield yellow crystals of the title compound suitable for X-ray diffraction.

S2. Refinement
H atoms were localized from difference maps but were modelled in calculated positions and treated as riding on their parent atom with C-H = 0.93 Å (aromatic), C-H = 0.97 Å (methylene) with U iso (H) = 1.2U eq (C aromatic or C methylene ).

Figure 1
The molecular structures of the entities in the title compound. Displacement ellipsoids are drawn at the 50% probability level; H atoms are represented as small spheres of arbitrary radius. Non-labelled atoms are generated by symmetry code 2 − x, y, 3/2 − z for the cation and by symmetry code 2 − x, y, 1/2 − z for the anion. The polymeric anionic [HgCl 1/1 Cl 4/2 ] − chain defined by long Hg-Cl distances (in dashed lines).

Figure 3
The The crystal packing of the title compound viewed down [001] (chain direction).

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