Sulfur cation radicals
Pure and Applied Chemistry
The oxidation potentials of 2-silylated and 2-stannylated 1,3-dithianes have been determined by cyclic voltammetry. There is substantial, geometrydependent, lowering of the oxidation potential by tin substituents as illustrated by 2,2-bis(trimethylstannyl)-1,3-dithiane whose oxidation potential of 0.19V is almost 1V lower than that of 1,3-dithiane itself. The UV He I photoelectron spectrum of this compound shows that its two lowest ionization potentials of 7.48 and 7.97 eV are about 1 eV lower
... han those of 1,3-dithiane. X-ray crystallographic structure studies on 2,2-bis(trimethylstannyl)-l,3-dithiane reveal that it adopts a chair conformation with an axial and an equatorial tin substituent. Variable temperature 13C N M R spectroscopic studies demonstrate that this compound undergoes ring inversion in solution with a barrier of approximately 13.5 kcal/mol. Aliphatic sulfur cation radicals, R, S' !, are novel reactive intermediates that are formed on oneelectron oxidation of dialkyl thioethers. The factors that control such electron-transfer and the stability of the sulfur cation radicals obtained are of interest. Metals and metalloids adjacent to the sulfur atom of thioethers may facilitate electron-transfer from the thioether and stabilize the sulfur cation radical obtained. This stabilization may result from bridging as shown in 1, hyperconjugation between the carbon-metal a-bond and sulfur p-orbital as shown in 2 which requires the interacting bond and orbital to be coplanar, or inductive effects.