High-valent diiron oxo species: key intermediates in challenging oxidations
Résumé
Bioinspired approach is a promising strategy to design powerful oxidizing catalysts. Cytochrome P-450 and methane monooxygenase (MMO) efficiently catalyze challenging reactions, e.g. oxidation of strong C-H bonds, using mononuclear iron porphyrin and non-heme diiron sites, respectively.
We have proposed a novel concept: to use diiron catalytic site like in soluble MMO but in macrocyclic ligand environment like in cytochrome P-450.Although metal phthalocyanine and porphyrin complexes are widely used in many catalytic applications and their catalytic chemistry is well-documented, their dimeric counterparts, in particular, µ-nitrido diiron complexes have not been considered as catalysts until recently. Quite unexpectedly, some single-atom bridged diiron complexes are capable of reacting with oxidants retaining their dimeric structure to form ultra high-valent diiron species. These short-living species were detected and characterized by UV-vis, EPR, ESI-MS, Fe K edge EXAFS, XANES and Mössbauer techniques. Of particular interest are the unusual catalytic properties of these highly electrophilic species which are able to oxidize methane and to perform oxidative transformation of the aromatic C-F bonds under very mild condions.