VIBRATIONAL-SPECTRA AND GAS-PHASE STRUCTURES OF FLUORINE FLUOROSULFATE (FOSO2F) AND CHLORINE FLUOROSULFATE (CLOSO2F)

Infrared spectra in the gaseous state, and in the matrix and Raman spectra in the solid state, were recorded for the halogen fluorosulfates XOSO(2)F, X = F, Cl. The absence of frequency splittings in the matrix spectra demonstrates the presence of one single conformer for both compounds. The assignments of the fundamental vibrations are supported by normal coordinate analyses based on frequencies and isotopic shifts. The molecular structures of both compounds were determined by gas electron diffraction (GED) and ab initio calculations (HF/3-21G* and HF/6-31G*). According to the GED analysis and in agreement with the ab initio calculations gauche conformers with dihedral angles tau(FSOX) approximate to 70 degrees are preferred in both fluorosulfates. The calculations predict the trans forms, tau(FSOX) approximate to 180 degrees, to be higher in energy by about 10 kJ mol(-1) for X = F and by about 8 kJ mol(-1) for X = Cl.