Comparison of the Thermal, Photochemical and Mass Spectrometric Fragmentation of Sulphur Heterocycles with cis‐Dithioethene‐Structure
The mass spectrometric primary fragmentation of 3‐methylthio‐1,4,2‐dithiazines 1, 1,4‐dithiins 2, 2,3‐dihydro‐1,4‐dithiin‐2‐ones 4, 1,3‐dithiole‐2‐ones 5, 2‐imino‐1,3‐dithioles 6 and 1,3‐dithiole‐2‐thiones 7 is compared with their thermolytical and photochemical reaction. In the mass spectra an intense peak of the dithiete radical ion is observed, if in the compounds an energetically favourable neutral molecule is preformed: in 1 methyl rhodanide, in 3 ethene, in 4 ketene, in 5 carbon monoxide and in 6 hydrogen cyanide. The substances 1, 3–6 – with the restriction by 3 – yield photochemically the dithiete, too. The photolysis of dithiazines 1 is wave length dependent. Mass spectrometrically, thermally and photochemically the dithiins 2 form thiophenes. The dithiolethiones 7 decompose mass spectrometrically and thermally into carbon disulfide, sulfur and ethynes, but photochemically they form tetrathiafulvalenes. The fragmentation of the compounds 1–6 is analogous in mass spectrometry and photolysis; 2, 3, 5 and with reservation 1 show similar mass spectrometric, thermal and photochemical reactivity. Possible reasons for these analogies are discussed. The dithietes, generated by photolysis of the compounds 1, 4, 5 or 6 react with iron penta‐, nickel tetra‐, molybdenum hexa‐ and tungsten hexacarbonyl in preparative scale to the corresponding dithiolene complexes.