Vibrational Spectra and Gas Phase Structure of N-Cyanoimidosulfurous Difluoride, NCNSF₂

Abstract

The vibrational spectra, IR (gas) and Raman (liquid) of N-cyanoimidosulfurous difluoride, NCN=SF2, were recorded, and the molecular structure was determined by gas electron diffraction. The spectra were assigned by comparing the vibrational frequencies with those in related molecules and with calculated (HF, MP2, B3LYP with 6-31G(d) basis sets) values, and a normal coordinate analysis was performed. The molecule possesses a syn conformation (Ctriple bondN syn with respect to the bisector of the SF2 angle). This has been rationalized by orbital interactions of the electron lone pairs of sulfur and nitrogen with the N-C and S-F bonds, respectively, which are antiperiplanar or anticlinal to these lone pairs (anomeric effects). Quantum chemical calculations with the B3LYP and MP2 methods reproduce the experimental structure reasonably well if large basis sets (6-311G(2d,f)) are used.

Structures and Conformations of ((Trifluoroacetyl)imido)(trifluoromethyl)sulfur Fluoride, CF3C(O)NS(F)CF3

“…In the prevailing anti-syn form the S-C bond is orientated antiperiplanar and the S-F bond nearly perpendicular with respect to the N-C bond (φ(CsNdSsC) ) -164(5)°and φ(CsNd SsF) ) 98(4)°). The NdS bond in 1 and 2 (1.549(5) and 1.554(8) Å, respectively) is much longer than that in imidosulfurous difluorides (1.48 ( 0.01 Å) [1][2][3][4][5][6][7] and in dichlorides (1.515 ( 0.005 Å). 8,9 The lengthening of this bond can be attributed partially to the lower electronegativity of the substituents and partially to the absence of anomeric interactions in the anti-syn conformer.…”

“…All imidosulfurous difluorides of the type RNSF 2 with R = Cl, CF 3 , , NC, FC(O), CF 3 C(O), and FSO 2 7 as well as imidosulfurous dichlorides with R = CF 3 8 and FC(O) 9 possess syn conformation around the NS double bond (see Chart ). Although the anti form appears to be sterically more favorable, quantum chemical calculations predict its energy to be higher by about 5−10 kcal/mol than that of the syn conformer.…”

Anomeric Interactions in Pentafluoroethylimidosulfurous Dichloride, CF3CF2N=SCl2: Structural, Conformational and Configurational Properties in the Gaseous and Condensed Phases

“…Vibrational spectroscopy, gas electron diffraction, X‐ray crystallography, quantum chemical calculations, and other techniques have proved to be powerful tools to understand the structural properties of sulfur imide molecules containing fluorine atoms or fluorinated substituents groups. Thus, the structure and conformational and configurational properties of molecules of the type R F N=SF 2 [R F = CF 3 ,13–16 FC(O),17,18 NC,19 CF 3 C(O),20 and FSO 2 21,22] and R F N=SCl 2 [R F = CF 3 23,24 and FC(O)25] have been studied, all of which show only a ( Z ) configuration around the putative N=S double bond. It is interesting to note that compounds with different substituents attached at the sulfur atom of the N=S group favor the ( E ) form.…”

Vibrational Spectra and Gas-Phase Structure of N-Methyl-S,S-bis(trifluoromethyl)sulfimide, CH3NS(CF3)2

“…For imidosulfur difluorides of the type RNSF 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 SN 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.…”