Molecular structure of bis(trifluoromethyl)disulphide by gas electron diffraction

Abstract

The following structural parameters and estimated standard deviations (2σ) have been found for (CF₃S)₂: r_g(C—F) 1.333 (2)Å, r_g(C—S) 1.835 (5)Å, r_g(S—S) 2.030 (5)Å, ∠_α(F—C—F) 108.3 (0.3)°, ∠_α(S—S—C) 101.6 (0.6)°, dihedral angle (C—S—S—C) 104.4 (4.0)°. CF₃ groups are in essentially staggered conformations, and their axes are tilted by 5.0 (0.5)° away from the C—S bonds. Measured amplitudes of vibration agreed satisfactorily with those calculated from an approximate force field; shrinkage corrections were applied. The S—S bond is longer than expected from consideration of the electronegativity of CF₃ and the dimensions of other disulphides. Information on the barriers to internal rotation about C—S and S—S bonds derived from both diffraction and spectroscopic data is discussed. An explanation is proposed of the high barriers generally found in disulphides.