Reaction of Triplet Phenylnitrene with Molecular Oxygen

Triplet carbenes react with molecular oxygen with rates that approach diffusion control to carbonyl O-oxides, whereas triplet nitrenes react much slower. For investigating the reaction of phenylnitrene with O2, the nitrene was generated by flash vacuum thermolysis (FVT) of phenylazide and subsequently isolated in O2-doped matrices. FVT of the azide produces the nitrene in high yield and with only minor contaminations of the rearranged products that are frequently observed if the nitrene is produced by photolysis. The phenylnitrene was isolated in solid Ar, Xe, mixtures of these rare gases with O2, and even in pure solid O2. At temperatures between 30 and 35 K an extremely slow thermal reaction between the nitrene and O2 was observed, whereas at higher temperatures, solid Ar and O2 rapidly evaporate. Only O2-doped Xe matrices allowed us to anneal at temperatures above 40 K, and at these temperatures, the nitrene reacts with O2 to produce nitroso O-oxide mainly in its syn conformation. Upon visible light irradiation (450 nm), the nitroso oxide rapidly rearranges to nitrobenzene.