Cl/F-exchange reaction in COCl2/SbF5 system: A theoretical investigation

The mechanism and kinetic of a Cl/F-exchange SbF5-mediated reaction are studied for halocarbonyl COCl2 by means of theoretical calculations at the B3LYP level. Two energetic pathways are described in which antimony containing four-centre transition states are localized. The lowest energy barrier of 19.5 kcal/mol corresponds to a transition state in which the formally 16-valence electron triatomic ClCO+ species is linked to hexacoordinated SbF5Cl− anion. The rate constant for this Cl/F-exchange reaction is predicted by transition state theory and evaluated at kTST = 2.2 × 10−3 s−1 when T = 293 K.