The Missing Link: Triplet Fluorocarbonyl Nitrene FC(O)N

The elusive triplet fluorocarbonyl nitrene, FC(O)N (X3A′′), has been generated in high yield from matrix‐isolated FC(O)N3 by ArF excimer laser photolysis (λ=193 nm). As a side product FNCO was formed. The novel nitrene was characterized by IR, UV/Vis, EPR spectroscopy, and quantum‐chemical calculations. All six fundamental vibrations of FC(O)N at 1681.3, 1193.8, 879.8, 646.5, 588.7, and 434.8 cm−1 (argon matrix, 16 K), their 12/13C, 16/18O, and 14/15N isotopic shifts, and four electronic transitions at T0=13 890, 25 428, 29 166, and 30 900 cm−1 that exhibit vibrational fine structures have been detected. Under visible‐light irradiation at λ≥495 nm, FC(O)N reacted with molecular N2 in the matrix cage at 6 K to give back FC(O)N3, whereas near‐UV irradiation at λ≥335 nm yielded FNCO. The singlet–triplet energy gaps of different carbonyl nitrenes are discussed. The missing link! FC(O)N is the first triplet carbonyl nitrene that has now been fully characterized by IR (13C, 15N, 18O), UV/Vis, EPR spectroscopy, and its photochemistry (see picture).