Vibrational properties of some elusive members of the RNSO family: CF3NSO and SF5NSO

Abstract

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 DG values determine an equilibrium of 98.8% (syn) and 1.2% (anti) for CF3NSO, and 99% (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 bonds. The bonding properties of some RNSO and RNS(OF2 compounds are compared.