C-H Activation by an Iron-Nitrido Bis-Pocket Porphyrin Species

High-valent iron-nitrido species are nitrogen analogues of iron-oxo species which are versatile reagents for C-H oxidation. Nonetheless, C-H 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-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. C-H bonds with bond dissociation enthalpies (BDEs) of up to approximate to 84 kcal mol(-1) could be activated, and the second-order rate constants (k(2)) are on the order of 10(2)-10(4) s(-1) m(-1). The Fe-amido product formed after HAT could further release ammonia upon protonation.

Automated summary

In this study, the hydrogen atom transfer reactivity of an Fe porphyrin nitrido species towards C-H substrates was investigated using nanosecond laser flash photolysis. It was found that C-H bonds with bond dissociation enthalpies of up to approximately 84 kcal mol(-1) could be activated, with second-order rate constants on the order of 10(2)-10(4) s(-1) m(-1). The Fe-amido product formed after hydrogen atom transfer could further release ammonia upon protonation.