C-H Activation by Metal-Nitrido Species

Abstract

High-valent iron-nitrido species are nitrogen analogues of iron-oxo species which are versatile reagents for CÀH oxidation. Nonetheless, CÀH activation by iron-nitrido species has been scarcely explored, as this is often hampered by their instability and short lifetime in solutions. Herein, the hydrogen atom transfer (HAT) reactivity of an Fe porphyrin nitrido species (2 c) toward C À H substrates was studied in solutions at room temperature, which was achieved by nanosecond laser flash photolysis (LFP) of its Fe III -azido precursor (1 c) supported by a bulky bis-pocket porphyrin ligand. CÀH bonds with bond dissociation enthalpies (BDEs) of up to % 84 kcal mol À1 could be activated, and the second-order rate constants (k 2 ) are on the order of 10 2 -10 4 s À1 m À1 . The Fe-amido product formed after HAT could further release ammonia upon protonation.