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 β-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.