Pentafluoroethyliminosulfur difluoride, CF3CF2NSF2: Vibrational spectra and quantum chemical calculations

The vibrational spectra of pentafluoroethyliminosulfur difluoride, CF3CF2NSF2, were recorded in the gas phase with IR spectroscopy and in the liquid state with Raman spectroscopy. Quantum chemical calculations at the B3LYP (6-311+G(d) and 6-311+G(2df) basis sets) and MP2 levels of theory (6-31+G(d) and 6-311G(d) basis sets) were performed. According to all calculations the lowest energy conformer possesses C1 symmetry with syn orientation of the SF2 group relative to the CN bond and near-trans orientation of the CF3 group relative to the NS bond (syn-trans). Calculations predict the hypothetical presence of a second stable conformer with anti-orientation of the SF2 group (anti-trans) which, however, possesses considerably higher energy and is therefore not observed in the analysis of the experimental spectra. The vibrational spectra were assigned for a single conformer in agreement with these calculations.