Two polymorphs of a new mercury(II) N,N-dipropyldithiocarbamate represented by centrosymmetric binuclear and pseudo-binuclear molecules, [Hg2(PrDtc)4] (1) and [Hg(PrDtc)2]2 (2), have been isolated, identified using heteronuclear (13C, 15N) CP-MAS NMR and structurally characterised by single-crystal X-ray diffraction analysis. There are two pairs of inequivalent PrDtc ligands playing either terminal chelating or tridentate bridging structural functions in the former compound; while the latter complex comprises two pairs of structurally inequivalent chelating PrDtc ligands. The reaction of freshly precipitated mercury(II) N,N-dipropyldithiocarbamate (HgPrDtc) with a [AuCl4]−/2 M HCl solution results in the formation of the ionic complex [Au(PrDtc)2]2[Hg2Cl6] (3). There are two inequivalent centrosymmetric cations, [Au(PrDtc)2]+ (‘A’ and ‘B’), and a binuclear centrosymmetric anion, [Hg2Cl6]2− in the structure of 3. In the cationic part of the complex, each of the gold(III) cations has two pairs of the relatively weak inequivalent secondary Au···S bonds with two neighbours, therefore forming linear supramolecular cationic chains (⋯‘A’⋯‘B’⋯‘A’⋯‘B’⋯)n. To study the thermal behaviour of the compounds, simultaneous thermal analysis was also performed. The formation of HgS and reduced elemental gold was established during the thermolysis of 1/2 and 3, respectively.