Defluorination of HFCs by a Magnesium Reagent

Reaction of a series of HFCs with a nucleophilic main group reagent containing a Mg–Mg bond results in defluorination to form the corresponding magnesium fluoride complex. In the case of 1,1,1,2-tetrafluoroethane (HFC-134a) generation of the fluoride occurs alongside selective formation of 1,1-difluoroethene. This is a highly unusual reactivity pattern for HFC-134a, which more commonly reacts by deprotonation and HF elimination. DFT calculations have been carried out to better understand the selectivity and compare the barriers for sp3 C–F bond activation with sp3 C–H bond activation in this system.