Mercury(II) complexes of heterocyclic thiones.: Part 1. Preparation of 1:2 complexes of mercury(II) halides and pseudohalides with 3,4,5,6-tetrahydropyrimidine-2-thione. X-ray, thermal analysis and NMR studies

A series of complexes HgX2(H4pymtH)2 (X=Cl−, Br−, I−, SCN−, CN−; H4pymtH=3,4,5,6-tetrahydropyrimidine-2-thione) has been obtained by the reaction of H4pymtH with mercury(II) halides and pseudohalides in the molar ratio 2:1. X-ray diffraction studies revealed tetrahedral coordination of mercury with S-bound H4pymtH. The exception is Hg(CN)2(H4pymtH)2 where the coordination is 2+2 with two strongly bound CN− ligands and weaker HS bonds with H4pymtH. One- and two-dimensional 1H and 13C NMR measurements in dimethylsulfoxide solution confirmed the complexation of mercury to sulfur. The greatest complexation effects on chemical shifts were detected for the C-2, C-5 and H-1,3 atoms, i.e. two, four and five bonds away from mercury atom. The complexation effects in Hg(SCN)2(H4pymtH)2 and Hg(CN)2(H4pymtH)2 are in agreement with the strongest intramolecular H-bonding in the former and the weakest HgS bonds in the latter as compared to other complexes here.