Variable-Temperature Photoelectron Spectral Study of 1,3-Dithiol-2-one and 4,5-Disubstituted 1,3-Dithiol-2-ones. Thermal Generation of 1,2-Dithiete, 3,4-Disubstituted 1,2-Dithietes, and Dialkyl Tetrathiooxalates

Article abstract of DOI:10.1021/ja00352a004

The thermal fragmentation of 1,3-dithiol-2-one, its 4,5-dimethyl,dicyano, monocyclic 4,5-dialkylthio (R⁴ = R⁵ = SCH3, SC2H5, SCH(CH3)2), and bicyclic alkylthio derivatives (R^4,5 = SCH2S, S(CH2)2S, S(CH2)3S) was investigated by variable-temperature photoelectron spectroscopy and in part by the matrix-isolation technique and infrared spectroscopy.The photoelectron spectra of the reactive intermediates 1,2-dithiete, 3,4-dimethyl-1,2-dithiete, and diethyl tetrathiooxalate are presented and interpreted.The new reactive species are unambiguously identified by photoelectron spectral and quantum chemical means.In addition, the photoelectron spectra of the stable (i.e., isolable at room temperature) compounds 3,4-bis(trifluoromethyl)-1,2-dithiete, and diethyl tetrathiooxalate are discussed.The influence of substituents on the relative stabilities of the 1,2-dithiete vs. the 1,2-dithione structures is studied using the MNDO method.The theoretical as well as the experimental results show that 1,2-dithiete and 3,4-dimethyl-1,2-dithiete are thermodynamically favored above their 1,2-dithione counterparts.