Donor Stabilized Borylnitrene:  A Highly Reactive BN Analogue of Vinylidene

Abstract

A donor atom stabilized borylnitrene, 2-nitreno-1,3,2-benzodioxaborole 4c, is characterized by matrix isolation IR, UV, and ESR spectroscopy as well as multiconfiguration SCF and CI computations. UV irradiation (λ ) 254 nm) of the corresponding azide 6c, isolated in solid argon at 10 K, produces 4c in high yield. The oxygen donor atoms in 4c result in a triplet ground state (|D/hc| ) 1.492 cm -1 , |E/hc| ) 0.004 cm -1 ) for the borylnitrene. The lowest energy singlet state ( 1 A1) is 33 kcal mol -1 higher in energy and closely related to the ground state of vinylidene. Under the conditions of matrix isolation, triplet 4c is photochemically and thermally stable toward rearrangement to the corresponding cyclic iminoborane. Photochemical irradiation (λ > 550 nm) of 4c rather causes an efficient reaction with molecular nitrogen, lying in matrix sites nearby, to give 6c. Similarly, photochemical, but not thermal, trapping of 4c with CO is possible and results in the corresponding isocycanate 9c. Thermal reaction of 4c with O 2 in doped argon matrixes at 35 K could be observed by IR spectroscopy to result in borylnitroso-O-oxide 17c as shown by 18 O2 labeling experiments and DFT computations. The diradical 17c is very photolabile and quickly rearranges to the nitritoborane 16c upon irradiation.

Metal‐Free Conversion of Methane and Cycloalkanes to Amines and Amides by Employing a Borylnitrene

“…[20][21][22][23] Borylnitrenes 1 are transient species, which have been trapped successfully. [24] The recently characterized catechol derivative 1 a (Scheme 1), a triplet-ground-state nitrene obtained photochemically from the corresponding azidoborane 3 a under matrix-isolation conditions, [25] showed unusually high reactivity. We ascribed this to the electronic similarity between 1 a in its singlet state and difluorovinylidene, a "superelectrophilic" carbene that inserts into methane and dihydrogen at 20-40 K. [26] In order to investigate the reaction of 1 a with methane, we isolated azide 3 a in argon doped with methane (1-2 % CH 4 or CD 4 ) at 10 K. Photolysis of 3 a using UV irradiation (l = 254 nm) resulted in the complete disappearance of 3 a and the concomitant formation of nitrene 1 a according to the IR spectra.…”

The chemistry of nitroso oxides

“…Available literature data mainly concern aromatic nitroso oxides. There are only three examples of the formation of nonaromatic nitroso oxides, namely benzyl-O-nitroso oxide 66 , 2-nitroso oxido-1,3,2-benzodioxaborole 67 , and β-nitroso oxido-propiophenone 68 . We will not devote a special section to these species and they are discussed together with aromatic nitroso oxides.…”

“…Photolysis of azide 13 was carried out in an argon matrix at 10 K in the presence of oxygen 97 . On heating a matrix up to 35 K, the appearance of the bands, which according to computations were assigned to trans-isomer of nitroso oxide 14, was observed in the IR spectrum (equation 3).…”

“…An unusual product was found upon photochemical isomerization of nitroso oxide 14, which formed in the reaction of triplet borylnitrene 13 with oxygen in an argon matrix (equation 3) 97 . It turned out that upon irradiation of this nitroso oxide with light of wavelength 254 nm at 35 K nitritoborane 26 is produced (equation 6).…”

“…It is thermodynamically more stable than the corresponding dioxaziridine and nitroborane by 435 and 92 kJ mol −1 , respectively. The fact that photolysis of nitroso oxide 14 leads to the final product that is different from products of the analogous reaction of aromatic nitroso oxides is explained by the formation of the strong B-O bond in nitritoborane 26 97 .…”