Redetermination of poly[μ-chlorido-hepta-chlorido-μ(3)-l-proline-μ(2)-l-proline-tetra-mercury(II)].

The asymmetric unit of the title compound, [Hg(4)Cl(8)(C(5)H(9)NO(2))(2)](n), consists of four HgCl(2) units and two L-proline ligands in the zwitterionic form. In each HgCl(2) unit, the Hg(II) ion is strongly bonded to two Cl atoms, and the Hg(II) ions in two of the HgCl(2) units are chelated by O atoms of two l-proline ligands, with one strong and one weak Hg-O bond. In the crystal structure, HgCl(2) and L-proline units are linked to form an extended chain along the a axis. The chain structure is further stabilized by N-H⋯Cl hydrogen bonds, and the chains are arranged in layers parallel to the ab plane. The structure of the title compound was originally determined by Ehsan, Malik & Haider [(1996). J. Banglad. Acad. Sci.20, 175] but no three-dimensional coordinates are available.