Poly{guanidinium bis[dichloromercury(II)]-μ₄-chloro}

Both the [C(NH₂)₃]⁺ cations and the [Hg₂Cl₅]⁻ anions of the title compound occupy special positions on two different twofold axes, one passing through the central Cl atom of the anion (along [100]), the other along a C—N bond of the cation (along [010]). The coordination polyhedron around the Hg atom can be described as a distorted octahedron of six Cl atoms, with two short [2.306 (5) and 2.322 (4) Å], two long [2.905 (7) and 2.906 (7) Å] and two very long [3.271 (6) and 3.344 (6) Å] Hg—Cl distances. In the crystal structure, there are alternate layers of cations and polyanions. Taking the very long Hg—Cl contacts into account, the polyanions are built of Hg₂Cl₅⁻ units (which can be described as two HgCl₂ fragments connected via a chlorine anion), interconnected through the common square-planar coordinated Cl atom. Two factors act to stabilize the structure of the crystal, i.e. the electrostatic interaction between the adjacent layers and the network of N—H...Cl hydrogen bonds.

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