文摘
The vibrational spectra of N-(trifluoromethyl)sulfinylamine, CF3NSO and N-(pentafluorsulfanyl)sulfinylamine, SF5NSO have been recorded and assigned. According to quantum chemical calculations (B3LYP and MP2 with 6-31G(d) and 6-311+G(df) basis sets) the sterically unfavorable syn (Z-) conformers are 2.6-4.1 kcal/mol (CF3NSO) and 3.1-4.6 kcal/mol (SF5NSO) lower in free energy than the anti conformers. Such ¦¤G¡ã values determine an equilibrium of 98.8 % (syn) and 1.2 % (anti) for CF3NSO, and ¡Ö99 % (syn) and < 1 % (anti) for SF5NSO (B3LYP and MP2 with 6-311+G(df) basis set). The presence of a single conformer is confirmed by the vibrational spectra. The syn structure of RNSO compounds is stabilized by strong anomeric effects between the N and S electron lone pairs and the opposite NR and SO ¦Ò* bonds. The bonding properties of some RNSO and RNS(O)F2 compounds are compared.