Several polynuclear Hg(II) complexes containing the flexible ditopic bisimidazolylmethane ligand (C7H8N4, bim) have been prepared by reaction of equimolar quantities of mercury salts (acetate, cyanide, thiocyanate, chloride, and iodide) in EtOH or acetonitrile solution. Their crystal and molecular structures were retrieved from laboratory powder diffraction data, and their thermal properties were fully characterized, including the determination of the thermal expansion coefficients and the related strain tensor using thermodiffractometric methods. [Hg(bim)(CH3COO)(2)](2) consists of cyclic dimers with chelating acetates, while the [Hg(bim)X-2](n) species (X = Cl, CN, SCN, and I) are one-dimensional polymers, with dangling X groups. A further complex of nominal Hg-2(bim)Cl-2 formulation was also prepared, but the complexity and nonideality of its powder diffraction traces prevented the determination of its main structural features.