Sulfur cation radicals

The oxidation potentials of 2-silylated and 2-stannylated 1,3-dithianes have been determined by cyclic voltammetry. There is substantial, geometry-dependent, lowering of the oxidation potential by tin substituants as illustrated by 2,2-bis(trimethylstannyl)-1,3-dithiane whose oxidation potential of 0.19V is almost IV 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 than those of 1,3-dithiane. X-ray crystallographic structure studies on 2,2-bis(trimethylstannyl)-1,3-dithiane reveal that it adopts a chair conformation with an axial and an equatorial tin substituent. Variable temperature ¹³C NMR spectroscopic studies demonstrate that this compound undergoes ring inversion in solution with a barrier of approximately 13.5 kcal/mol.