Ligand field effects on the ground and excited states of reactive FeO species.

High-valent Fe(iv)-oxo species have been found to be key oxidizing intermediates in the mechanisms of mononuclear iron heme and non-heme enzymes that can functionalize strong C-H bonds. Biomimetic Fe(iv)-oxo molecular complexes have been successfully synthesized and characterized, but their catalytic reactivity is typically lower than that of the enzymatic analogues. The C-H activation step proceeds through two competitive mechanisms, named σ- and π-channels.