Direct Observation of a Nonheme Iron(IV)–Oxo Complex That Mediates Aromatic C–F Hydroxylation

The synthesis of
a pentadentate ligand with strategically designed
fluorinated arene groups in the second coordination sphere of a nonheme
iron center is reported. The oxidatively resistant fluorine substituents
allow for the trapping and characterization of an FeIV(O)
complex at −20 °C. Upon warming of the FeIV(O) complex, an unprecedented arene C–F hydroxylation reaction
occurs. Computational studies support the finding that substrate orientation
is a critical factor in the observed reactivity. This work not only
gives rare direct evidence for the participation of an FeIV(O) species in arene hydroxylation but also provides the first example
of a high-valent iron–oxo complex that mediates aromatic C–F
hydroxylation.