Synthesis and characterisation of zinc, cadmium and mercury complexes of benzilbisthiosemicarbazone. Structure of cadmium derivative

Complexes [MLH6(NO3)2] (M=Cd, Hg) (1 and 2), [MLH4] (M=Hg, Zn) (3 and 5) and [ZnLH5NO3] (4) have been synthesised by reaction of benzilbisthiosemicarbazone LH6 with cadmium, mercury and zinc nitrates in ethanol. The X-ray diffraction study of cadmium complex 1 shows that the azomethine nitrogen atoms, the sulfur atoms and the nitrate groups are bonded to the cadmium atom giving, the first time for this kind of ligands, a distorted octahedral geometry. Complexes have been characterised by elemental analyses and mass spectra as well as by IR, 1H, 13C and 113Cd NMR and 13C and 113Cd CP/MAS NMR spectroscopies. In all complexes LH6 acts as a tetradentate N2S2 ligand. The electrochemical behaviour of complexes, studied by cyclic voltammetry, shows metal centred and ligand reduction processes for all of them.