Preparation and Properties of Chlorosulfuryl Chloroformate, ClC(O)OSO₂Cl

The novel chlorosulfuryl chloroformate, ClC(O)OSO₂Cl, was prepared by the reaction of CCl₄ and SO₃. Alternatively, the compound was obtained from the direct insertion reaction of SO₃ to Cl₂C═O. The latter reaction constitutes also a confirmation of the proposed mechanism for the former one. Density functional theory and MP2 theoretical approximations predict the existence of two conformers, syn-gauche and syn-anti, depending on the value adopted by the dihedral angles ϕ(Cl-C-O-S) and ϕ(C-O-S-Cl). The structure of the syn-gauche conformer was determined by gas-phase electron diffraction (GED). The existence of the syn-anti conformer can be neither confirmed nor excluded by the GED experiment. Vibrational spectra (vapor-phase and argon-matrix Fourier transform infrared and liquid Fourier transform Raman) were interpreted by an equilibrium mixture between both conformers.