Complexes of heterocyclic thiones and Group 12 metals: Part 5. Reactions of 1,3-thiazolidine-2-thione and benzo-1,3-thiazoline-2-thione with mercury(II) halides in a 2:1 ratio. Crystal structures of bis(1,3-thiazolidine-2-thione) mercury(II) bromide and b

Reactions of mercury(II) halides with 1,3-thiazolidine-2-thione (tzdSH) and benzo-1,3-thiazoline-2-thione (bztzSH) in aqueous ethanol produced the 1:2 complexes with the former ligand but, due to steric effects, only the previously described 1:1 complexes of the latter were isolated. Vibrational and 13C NMR spectral studies indicate η1-thione donation by the heterocyclic ligand and this has been confirmed by the crystal structure determination of (tzdSH)2HgBr2. The structure consists of pseudotetrahedral mercury (II) with longer C–S and shorter C–N bonds than in the free ligand and with the Br–Hg–Br angle being ∼20° smaller than the largest angle, S–Hg–S, around mercury due to deformation by inter- and intra-molecular interactions. The heterocyclic ligands are unsymmetrical round mercury relative to the two bromines. Reaction of the two thiones with mercury(II) acetate in ethanol in the presence of triethylamine results in deprotonation with the formation of the corresponding thionates. The former produced insoluble (tzdS)2Hg while the latter formed plate-like (bztzS)2Hg whose crystal structure showed linearity around mercury with digonal coordination via the thionate sulphur. The small Hg–S–C angle and Hg⋯N separation are indicative of a weak interaction between mercury and the nitrogen of the thioamide double bond.