Novel mercury(II) complexes of 1,3-dithiole-2-thiones containing the 2-pyridyl moiety: syntheses, X-ray crystal structures and solution behavior

The mercury(II) complexes of 5-pyridin-2-yl-5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiin-2-thione (2PyEDT-DTT: 1), [Hg(2PyEDT-DTT)X2] (X=Cl (2a), Br (2b) and I (2c)) were obtained from the reaction of HgX2 and 2PyEDT-DTT. These complexes adopt a dimeric arrangement of [Hg(2PyEDT-DTT)X2]2 through intermolecular Hg⋯N and Hg⋯S interactions. According to the FT-IR/UV–Vis/NMR spectroscopy data, these intermolecular interactions are cleaved in media containing trace H2O. [Hg(2PyDT-DTT)2] (3; 2PyDT-DTT: 5-(1-pyridin-2-yl-vinylsulfanyl)-2-thioxo-[1,3]dithiole-4-thiolate) was isolated from the filtrate of 2. The Hg(II) ion is located in a center of symmetry and adopts a distorted octahedral geometry with four sulfur atoms (two from the thiolate groups and two from the sulfide groups) and two nitrogen atoms from the pyridyl group. The time-dependent solution UV–Vis and 1H NMR measurements showed the transformation of 2PyDT-DTT to 2PyEDT-DTT caused by trace H2O in organic solvents.