Structure and conformational properties of carbonylbisimidosulfuryl fluoride, OC(NS(O)F 2) 2

Abstract

The molecular structure and conformational properties of OC(NS(O)F 2) 2 (carbonylbisimidosulfuryl fluoride) were determined by gas electron diffraction (GED) and quantumchemical calculations (HF/3-21G* and B3LYP/6-31G*). The analysis of the GED intensities resulted in a mixture of 76(12)% syn– syn and 24(12)% syn– anti conformer (Δ H 0= H 0( syn– anti)− H 0( syn– syn)=1.11(32) kcal mol −1) which is in agreement with the interpretation of the IR spectra (68(5)% syn– syn and 32(5)% syn– anti, Δ H 0=0.87(11) kcal mol −1). syn and anti describe the orientation of the SN bonds relative to the CO bond. In both conformers the SO bonds of the two NS(O)F 2 groups are trans to the C–N bonds. According to the theoretical calculations, structures with cis orientation of an SO bond with respect to a C–N bond do not correspond to minima on the energy hyperface. The HF/3-21G* approximation predicts preference of the syn– anti structure (Δ E=−0.11 kcal mol −1) and the B3LYP/6-31G* method results in an energy difference (Δ E=1.85 kcal mol −1) which is slightly larger than the experimental values. The following geometric parameters for the OC(NS) 2 skeleton were derived ( r a values with 3 σ uncertainties): CO 1.193 (9) Å, C–N 1.365 (9) Å, SN 1.466 (5) Å, OC–N 125.1 (6)° and C–NS 125.3 (10)°. The geometric parameters are reproduced satisfactorily by the HF/3-21G* approximation, except for the C–NS angle which is too large by ca. 6°. The B3LYP method predicts all bonds to be too long by 0.02–0.05 Å and the C–NS angle to be too small by ca. 4°.