Characterization of a Byproduct in the Alkylation of DMIT: Alkylation on the Least Nucleophilic Sulfur Atom

It is generally accepted that the alkylation of (Et 4 N) 2 [Zn(DMIT) 2 ] ( 1 ) is a very clean reaction that produces 4,5‐bis(alkylthio)‐1,3‐dithiole‐2‐thiones 4 in very high yields. Although this procedure has been widely used, we have found that, in addition to the 4,5‐bis(alkylthio)‐1,3‐dithiole‐2‐thione products 4 , highly unexpected byproducts are formed during the alkylation reaction in which the thione functionalities of DMIT in (Et 4 N) 2 [Zn(DMIT) 2 ] ( 1 ) are alkylated instead of the more reactive thiolate groups. These byproducts were identified as a novel type of compounds, namely bis(2‐alkylthio‐1,3‐dithiol‐1‐ium‐4,5‐dithiolato)zinc compounds 3 , being composed of two identical 2‐alkylthio‐1,3‐dithiol‐1‐ium‐4,5‐dithiolate moieties coordinated to a single zinc(II) atom and were characterized by elemental analyses and different spectroscopic techniques as well as single‐crystal X‐ray structure analyses. A comparison of the physical properties of compounds 3 and (Et 4 N) 2 [Zn(DMIT) 2 ] ( 1 ) has been carried out. The outcome of these investigations revealed significant differences in the physical properties of these two systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)