Synthesis and molecular structures of methyl and phenylmercury(II) complexes with benzaldehyde-4,4-dimethylthiosemicarbazone

The reactions of benzaldehyde-4,4-dimethylthiosemicarbazone (LH) with methyl and phenylmercury (II) chlorides in different conditions were investigated. From the methyl derivative, two complexes [HgMeClLH] (1) and [HgMeL] (2), were obtained working in ethanol in the absence or the presence of basic medium respectively. However, in the same conditions only the complex [HgPhL] (3) was isolated. The corresponding complex containing the neutral ligand [HgPhClLH] (4) was prepared in refluxing dicloromethane. Furthermore, in the presence of hydrochloric acid, HgPhCl undergoes a symmetrization reaction to afford HgPh2 and [Hg(LH)2(μ-Cl)2HgCl2], reported previously from the reaction with HgCl2. Spectroscopic studies and X-ray structural analysis showed that the thiosemicarbazone is always SN coordinated, giving a distorted tetrahedral arrangement in complexes 1 and 4 and a distorted T-shaped stereochemistry around the mercury centre in complexes 2 and 3.

Graphical abstractReaction of organomercury(II) salts with a benzaldehyde-based thiosemicarbazone ligand yielded complexes showing three and four-coordinate environments. In the complexes with HgMeCl the ligand charge can be controlled by addition of base while in HgPhCl derivatives it is possible by choosing the appropriated solvent.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Organomercury complexes with a benzaldehyde thiosemicarbazone ligand were synthesized. ► In the methyl derivatives the ligand deprotonation can be induced by adding LiOH.H2O. ► In the phenyl derivatives the ligand charge can be controlled choosing the solvent. ► In complexes with the neutral ligand the mercury is four-coordinate. ► In complexes with the deprotonated ligand the mercury is three-coordinate.