Spectral and structural studies of mercury(II) complexes of 2-pyridineformamide N(4)-dimethylthiosemicarbazone

Reaction of 2-pyridineformamide N(4)-dimethylthiosemicarbazone (HAm4DM) with halides of mercury(II) directly afforded complexes of the form [Hg(HAm4DM)X-2] (X = Cl, Br or I). In all these new compounds, which were characterized by elemental analysis, IR spectroscopy and H-1, C-13, and, when possible, Hg-199 NMR spectroscopy, the ligand coordinates through its sulfur atom and pyridine and azomethine nitrogen atoms, as was confirmed by X-ray diffraction studies in the case of [Hg(HAm4DM)Br-2].DMSO. Ethanolic solutions of [Hg(Am4DM)Cl-2] and [Hg(Am4DM)Br-2] afforded crystals of [Hg(Am4DM)Cl](2) and [Hg(Am4DM)Br](2), the structures of which were also studied by single-crystal X-ray diffractometry. In these two compounds the anionic ligand, Am4DM(-), coordinates to one Hg through pyridine nitrogen, imine nitrogen and thiolato sulfur atoms, the last of which bridges to the other Hg via a bond that is shorter than the chelating Hg-S bond. Thus all three of the complexes studied by Xray diffractometry have pentacoordinated Hg centre and in all three cases the coordination polyhedron is closer to a square pyramid than to a trigonal bipyramid. (C) 2003 Elsevier Science Ltd. All rights reserved.