Studies on transition-metal 4,5-dimercapto-1,3-dithiole-2-one (DMID) complexes. Preparation and characterization

A series of integer or non-integer oxidation-state metal complexes of the multi-sulfur donor ligand 4,5-dimercapto-1,3-dithiole-2-one (DMID) with Ni(II), Cu(II) and Zn(II) has been prepared by precipitating them as tetrabutylammonium, tetraethylammonium, or tetramethylammonium salts. The compounds are characterized by negative-ion fast atom bombardment mass spectral analysis, Fourier transform IR spectral analysis and UV-Vis spectral analysis. Synthetic studies reveal that the stoichiometry of the complex depends not only on the nature of the counter cation, but also on the aerial-oxidation time after the addition of the counter cation and on the nature of the central chelating metal ion. The electronic spectral studies of the complexes with those of related compounds reveal that there are strong π-d interactions in the Ni-chelating species. As an important starting material, the synthesis of 1,3,4,6-tetrathiapentalene-2,5-dione is studied in detail as well.