Unusual Nitrene Oxidation Product Formation by Metathesis Involving the Dioxygen O−O and Borylnitrene B−N Bonds. Issue 55 (9th September 2020)

• Record Type: Journal Article
• Authors: Bhagat, Virinder; Schumann, Julia; Bettinger, Holger F.
• Is Part Of: Chemistry. Volume 26:Issue 55(2020)
• Page Start: 12654
• Page End: 12663
• Publication Date: 2020-09-09
• Subjects: boron -- density functional calculations -- nitrenes -- radicals -- reaction mechanisms; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202002445
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The reaction of dioxygen with nitrenes can have significant energy barriers, although both reactants are triplet diradicals and the formation of nitroso‐ O ‐oxides is spin‐allowed. By means of matrix‐isolation infrared spectroscopy in solid argon, nitrogen, and neon, and through high‐level computational quantum chemistry, it is shown herein that a 3‐nitreno‐1, 3, 2‐benzodioxaborole CatBN (Cat=catecholato) reacts with dioxygen under cryogenic conditions thermally at temperatures as low as 7 K to produce two distinct products, an anti ‐nitroso‐ O ‐oxide and a nitritoborane CatBONO. The computed barriers for the formation of nitroso‐ O ‐oxide isomers are very low. Whereas anti ‐nitroso‐ O ‐oxide is kinetically trapped, its bisected isomer has a very low barrier for metathesis, yielding the CatBO+NO radicals in a strongly exothermic reaction; these radicals can combine under matrix‐isolation conditions to give nitritoborane CatBONO. The trapped isomer, anti ‐nitroso‐ O ‐oxide, can form the nitritoborane CatBONO only after photoexcitation, possibly involving isomerization to the bisected isomer of anti ‐nitroso‐ O ‐oxide. Abstract : Overcoming barriers : The reaction of dioxygen with nitrenes can have significant energy barriers. The reaction mechanism of borylnitrene 1 is investigated through matrix‐isolation infrared spectroscopy and high‐level computational quantum chemistry. Borylnitrene 1 reacts with dioxygen to form nitritoborane 3 a via nitroso‐ O ‐oxide isomer 2 c . Nitroso‐ O ‐oxide isomer 2 a is stable towards thermal reaction to 3 a, but dyotropic rearrangement can be achieved photochemically.