(1) exhibits an infinite zigzag chain in which each mercury(II) atom is coordinated by pairs of carboxylate oxygen atoms and chloride ligands in a distorted tetrahedral geometry. In complex (2), the mercury(II) atom is in an unusual square-planar coordination geometry, and weak mercury-ligand and hydrogen bonding extend the structural skeletons into a three-dimensional network. Complex (3) consists primarily of an assembly of HgCh(HL I) moieties and [Hg2CI6]-anions, and the mercury(II) atoms are in planar T-shaped and distorted tetrahedral coordination environments, respectively. The resulting three-dimensional network is based on the cross-linkage of nearly planar, wide ribbons running in the a direction.KEY WORDS: Mercury(ll) dicarboxylate; double betaine; 1,4-diazoniobicyclol2.2.2loctane-l,4 diacetate; X-ray crystallography; polymeric structure.