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) A. Two additional longer distances [Hg⋯Cl = 3.104 (14) A] 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) A.