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(H(4)pymtH)(2) (X = Cl-, Br-, I-, SCN-, CN-; H(4) pymtH = 3,4,5,6-tetrahydropyrimidine-2-thione) has been obtained by the rea ction of H(4)pymtH with mercury(II) halides and pseudohalides in the molar ratio 2:1. X-ray diffraction studies revealed tetrahedral coordination of m ercury with S-bound H(4)pymtH. The exception is Hg(CN)(2)(H(4)pymtH)(2) whe re the coordination is 2+2 with two strongly bound CN- ligands and weaker H -S bonds with H(4)pymtH. One- and two-dimensional H-1 and C-13 NMR measurem ents 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)(H(4)pymtH)(2) and Hg(C N)(2)(H(4)pymtH)(2) are in agreement with the strongest intramolecular H-bo nding in the former and the weakest Hg-S bonds in the latter as compared to other complexes here. (C) 2000 Elsevier Science S.A. All rights reserved.