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 bis(benzo-1,3-thiazolinato)mercury(II)

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 C-13 NMR spectral studies indicate eta (1)-thione donation by the heterocyclic ligand and this has been confirmed by the crystal structure determination of (tzdSH)(2)HgBr2. 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 similar to 20 degrees 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)(2)Hg while the latter formed plate-like (bztzS)(2)Hg whose crystal structure showed linearity around mercury with digonal coordination via the thionate sulphur. The small Hg-S-C angle and (HgN)-N-... separation are indicative of a weak interaction between mercury and the nitrogen of the thioamide double bond. (C) 2001 Elsevier Science B.V. All rights reserved.