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.