First example of a preferred anti configuration in RN = SX2 compounds: N -fluoroformyliminotrifluoromethylsulfur fluoride, FC(O)N = S(F)CF3

The vibrational spectra, including Raman spectra at different temperatures and resonance Raman spectra, and theoretical calculations of N-fluoroformyl iminotrifluoromethylsulfur fluoride, FC(O)N=S(F)CF3, were obtained and inte rpreted. They point to the existence of a predominant anti-syn form and in equilibrium at lower concentration a syn-syn form (the first related to the nitrogen lone pair with respect to the sulfur lone pair and the second is related to the C=O double bond with respect to the N=S double bond). The ge neral result indicates that it is the first anti configuration reported for this type of molecule implying for the energetically most favoured form an anti configuration of the lone pairs attached to both the S and N atoms. C opyright (C) 2000 John Wiley & Sons, Ltd.