Carbon subsulfide C3S2 – synthesis by flash vacuum pyrolysis and crystal structure determination

Abstract

Abstract Carbon subsulfide C3S2 can be produced on a preparative scale by flash vacuum pyrolysis (FVP). The precursor 5-(methylthio)-3H-1,2-dithiole-3-thione (C4H4S4) proved to be particularly suitable and yields up to 8% could be achieved on evaporation at T = 180 °C and pyrolysis of the vapour at 950 °C. The other precursors tested, C4S6 and C6S8, were far less productive. Insight into the thermal conversion of C4S6 was gained by isolation and structure determination of a new isomer of the sulur-carbon compound C8S8, which is formed on thermal treatment of C4S6 at T = 330 °C. The formation of C8S8 can be interpreted by sulfur cleavage from C4S6. Crystal growth by sublimation below 0 °C allowed for the determination of the crystal structure of C3S2. The five-atomic molecules are linear and arranged in a typical pattern analogous to the crystal structures of I2, CS2 and CSe2. The reaction of C3S2 with bromine is known to give C3Br6S2 of yet unknown structure. By sublimation of C3Br6S2 in air, 4,5-dibromo-1,2-dithiol-3-one (C3Br2OS2) was obtained, representing the product of bromine abstraction and oxidation. This substantiates the former suggestion for C3Br6S2 to have the structure of a hexabromodithiolane.