“…For imidosulfur difluorides of the type RNSF 2 with R = Cl, CF 3 , , SF 5 , CN, FC(O), CF 3 C(O), and FSO 2 , whose gas-phase structures have been determined, only the syn configuration around the SN double bond was observed (see Chart ). This sterically unfavorable configuration is stabilized by orbital interactions of the sulfur and nitrogen lone pairs with the opposite N−R and S−F antibonding σ* orbitals, respectively.…”
The molecular structure of N-methyl-S,S-bis(trifluoromethyl)sulfimide, CH3N=S(CF3)2, was determined by gas electron diffraction and quantum chemical calculations [B3LYP and MP2 with 6-31+G(2df,p) basis sets]. Furthermore, vibrational spectra, IR (gas) and Raman (liquid), were recorded. These spectra were assigned by comparison with analogous molecules and with calculated frequencies and intensities (HF, B3LYP, and MP2 with 6-311G basis sets). All experimental data and computational methods result in a single conformer with syn orientation of the CH3 group relative to the bisector of the two CF3 groups. The molecule possesses C1 symmetry, slightly distorted from CS symmetry. The N=S bond length in this compound [1.522(10) A] is longer than that in imidosulfur difluorides RN=SF2 [1.476(4) A - 1.487(5) A].
“…For imidosulfur difluorides of the type RNSF 2 with R = Cl, CF 3 , , SF 5 , CN, FC(O), CF 3 C(O), and FSO 2 , whose gas-phase structures have been determined, only the syn configuration around the SN double bond was observed (see Chart ). This sterically unfavorable configuration is stabilized by orbital interactions of the sulfur and nitrogen lone pairs with the opposite N−R and S−F antibonding σ* orbitals, respectively.…”
The molecular structure of N-methyl-S,S-bis(trifluoromethyl)sulfimide, CH3N=S(CF3)2, was determined by gas electron diffraction and quantum chemical calculations [B3LYP and MP2 with 6-31+G(2df,p) basis sets]. Furthermore, vibrational spectra, IR (gas) and Raman (liquid), were recorded. These spectra were assigned by comparison with analogous molecules and with calculated frequencies and intensities (HF, B3LYP, and MP2 with 6-311G basis sets). All experimental data and computational methods result in a single conformer with syn orientation of the CH3 group relative to the bisector of the two CF3 groups. The molecule possesses C1 symmetry, slightly distorted from CS symmetry. The N=S bond length in this compound [1.522(10) A] is longer than that in imidosulfur difluorides RN=SF2 [1.476(4) A - 1.487(5) A].
“…All imidosulfurous difluorides of the type RNSF 2 with R = Cl, CF 3 , NC, SF 5 , FC(O), CF 3 C(O), and SO 2 F whose gas-phase structures have been determined possess syn conformation around the NS bond (substituent R synperiplanar with respect to the SF 2 bisector). The only imidosulfurous dichloride, CF 3 NSCl 2 , whose structure was determined in the gas phase also possesses a syn structure.…”
The IR (gas) and Raman (liquid) spectra of FC(O)NSCl(2) demonstrate the presence of a conformational mixture in both phases. According to a gas electron diffraction study, the main conformer (94(8)%) possesses a syn-syn structure (C(O)F group synperiplanar with respect to the SCl(2) bisector and the C=O bond synperiplanar to the N=S bond). Quantum chemical calculations (HF, B3LYP and MP2 with 6-31G basis set, and MP2/6-311(2df)) predict a syn-anti structure for the second conformer. Analysis of the IR (gas) spectrum results in a contribution of 5(1)% of the minor form, corresponding to a Gibbs free energy difference DeltaG degrees = G degrees (syn-anti) - G degrees (syn-syn) = 1.75(15) kcal/mol. This value is reproduced very well by quantum chemical calculations, which include electron correlation effects (DeltaG degrees = 1.28-1.56 kcal/mol). The HF approximation overestimates this energy difference (DeltaG degrees = 3.24 kcal/mol).
“…Gas electron diffraction (GED) and/or microwave spectroscopy for sulfurdifluoride imides of the type RNSF 2 with RCl, CF 3 , , SF 5 , CN, FC(O), CF 3 C(O), and SFO 2 resulted in the presence of a syn configuration around the NS bond with the substituent R synperiplanar with respect to the bisector of the SF 2 group (see Chart ). 1 …”
The molecular structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide), SF5N=S(O)F2, have been studied by vibrational spectroscopy (IR (gas) and Raman (liquid)), by gas electron diffraction (GED), and by quantum chemical calculations (MP2 and B3LYP with (6-31G(d) and 6-311+G(2df) basis sets). According to GED, the prevailing conformer possesses a syn structure (N-SF5 bond synperiplanar with respect to the bisector of the SF2 group). Splitting of the symmetric N=S=O stretching vibration in gas and liquid spectra demonstrates the presence of a second conformer (11(5)%) with anticlinal orientation of the N-SF5 bond according to quantum chemical calculations. The geometric structure, conformational properties, and vibrational frequencies are well reproduced by quantum chemical calculations.
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