The gas-phase structure and conformational properties of N-sulfinylimine fluorocarbonylsulphane, FC(O)SNSO

Abstract

The conformational composition and geometric structure of FC(O)SNSO have been determined from electron diffraction intensities, vibrational spectra and ab initio calculations. The electron diffraction intensities can only be fitted by a mixture of two planar conformers with the CF bond trans or cis to the SN single bond. In both forms the CS single bond is trans to the NS double bond and the SN single bond is cis to the SO double bond. The conformational composition derived from the electron diffraction experiment, 85(5)% trans (Δ G°(ED) G°(cis) G°(trans)=1.0(2) kcal mol −1), is in excellent agreement with the value obtained from matrix IR spectra, 8% trans (Δ G°=1.1(1) kcal mol −1). Ab initio methods in the HF approximation predict slightly higher (HF/3-21G*) or lower (HF/6-31G*) values for the energy difference. Inclusion of electron correlation reproduces the experimental value perfectly. The following geometric parameters ( r a distances in Å and ∠ α angles in degrees with 3σ uncertainties) were derived for the predominant trans conformer: CO=1.178(5) Å, CF=1.342 Å (fixed), CS=1.760(16) Å, SN=1.689(14) Å, SN=1.549(7) Å, SO=1.449(3) Å, OCS=130.8(6)°, FCS=105.9(5)°, CSN=94.7(9)°, SNS=119.0(11)°, NSO=118.0(17)°. This experimental structure is reproduced reasonably well by HF/3-21G* calculations.