Structures and conformations of trifluoromethanesulfonic anhydride, (CF 3SO 2) 2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF 3SO 2) 2CF 2

Abstract

The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF 3SO 2) 2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF 3SO 2) 2CF 2 have been studied by gas electron diffraction (GED) and ab initio calculations ( HF 3–21 G∗ ). The calculations predict for both systems two stable conformers with C 2 symmetry and one with C 1 symmetry. In both compounds structures with C 2 symmetry and dihedral angles SOSC ≈ 100° ((CF 3SO 2) 2O) and SCSC ≈ 150° ((CF 3SO 2) 2CF 2) are lowest in energy. According to the GED analyses the dominant conformer of (CF 3SO 2) 2O possesses C 2 symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF 3SO 2) 2CF 2 only one conformer with C 2 symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given.