Aromatic C-F Bond Activation by Rare-Earth-Metal Complexes

C-F bond activation is a challenging reaction with increasing importance in synthesis. The strength of the C-F bond and the shielding effect of the fluorine atom render its activation difficult. Rare-earth metals offer an exceptional opportunity for this process because the high dissociation energy of the M-F bond offsets the strength of the C-F bond. Herein we report a unique reaction for the C-F activation of aromatic bonds by rare-earth-metal complexes. The strong C-F bond of perfluorobenzene is cleaved under reducing conditions in the presence of a rare-earth-metal iodide to form initially an equimolar mixture of a metal fluoride and a metal perfluorophenyl complex; the latter eventually undergoes beta-F elimination to a metal fluoride. A similar behavior is observed when inverse sandwich rare-earth-metal arene complexes react with perfluorobenzene. All compounds were characterized by X-ray crystallography, multinuclear NMR spectroscopy, and elemental analysis.