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

Abstract

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 1H, 13C, and, when possible, 199Hg 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 X-ray diffractometry have pentacoordinated Hg centre and in all three cases the coordination polyhedron is closer to a square pyramid than to a trigonal bipyramid.