Gas phase structure of trifluoromethyliminosulfurdifluoride, CF3NSF2, revisited

Abstract The gas phase structure of trifluoromethyliminosulfurdifluoride, CF 3 NSF 2 , was reinvestigated by a joint analysis of gas electron diffraction (GED) and microwave spectroscopy. Quantum chemical calculations were performed with the HF, MP2 and B3LYP methods using 6-31G ∗ basis sets. The GED intensities and MW rotational constants B and C were fitted best with a syn configuration (CF 3 group syn with respect to SF 2 ) and staggered orientation of the CF 3 group with large amplitude torsional motion around the C–N bond. The following skeletal geometric parameters ( r g distances and r α angles with 2 σ uncertainties) were derived: SN 1.477(6) A, S–F 1.594(2) A, N–C 1.409(8) A, C–NS 127.2(11)°, NS–F 112.7(10)° and F–S–F 92.8(4)°. The values for the SN and N–C distances and for the F–S–F angle differ appreciably from those derived in an earlier GED investigation. The HF approximation reproduces all bond lengths to within ±0.02 A and the MP2 and B3LYP calculations predict the SN and the S–F bonds to be longer. The bond angles are reproduced very well with all three methods.