Matrix photochemical study of XC(O)sy compounds (X : F, Cl; Y : NCO, CF3)

Abstract Matrix infrared spectra (4000–400 cm −1 ) have been recorded for (fluorocarbonyl)sulfenyl isocyanate, FC(O)SNCO, (fluorocarbonyl)trifluoromethylsulfane, FC(O)SCF 3 and (chlorocarbonyl)trifluoromethylsulfane, ClC(O)SCF 3 . Subsequent variable temperature and photochemical studies have been carried out. Both syn and anti forms have been identified in the gas phase for FC(O)SCF 3 , but the syn conformer is thermodynamically more stable than the anti rotamer. A randomization process is clearly observed when the compound isolated in Ar at cryogenic temperatures is irradiated with broad band UV–visible light. Both FC(O)SNCO and ClC(O)SCF 3 molecules show a single syn conformation. Moreover, for FC(O)SNCO matrix variable temperature deposition experiments and exposure of the matrix to broad band UV–visible light do not imply in changes revealing conformational equilibrium in the gas phase. For ClC(O)SCF 3 a photochemical test does not originate any interconversion. Although the decomposition of FC(O)SCF 3 and ClC(O)SCF 3 originates beside CO known compound (CF 3 SF and CF 3 SCl), the FC(O)SNCO could be used to isolate the hitherto unknown FSNCO species. For this molecule several theoretical calculations have been carried out to forecast its properties and structure.