Abstract:
Matrix isolation studies of the reactivity of a donor stabilized borylnitrene, 2-nitreno-1,3,2-benzodioxaborole (catBN; cat = catecholato), with reactants such as dioxygen (O2), carbon dioxide (CO2), ethene (C2H4), etc. were carried out which comprised of exploring the mechanistic aspects and product identification. The computational data obtained using density functional theory (DFT) and ab-initio methods corroborated the experimental results.
The matrix isolation studies of the thermal reaction of catBN with O2 resulted in the formation of two products: an anti-nitroso-O-oxide and a nitritoborane catBONO at temperatures as low as 7 K. In the next step, the irradiation with λ = 254 nm resulted in the conversion of previously formed anti-nitroso-O-oxide to catBONO. Computational studies were performed at a high level of theory to explain the experimental observation.
On the other hand, the photoreaction (λ > 550 nm) of matrix isolated catBN with CO2 resulted in a 1,2-oxaziridin-3-one derivative, catBNCO2. The computational and heavy isotope studies using the heavy isotopologues of CO2 showed that the CO vibrational mode is unusually shifted in 18O and 13C isotopologues of catBNO2 due to its involvement in Fermi resonance with ring deformation vibrational mode.
In a separate computational study, the high photoreactivity of catBN with closed-shell molecules upon λ > 550 nm irradiation was explained. The study showed that upon photoirradiation with λ > 550 nm, catBN relaxes to the lowest singlet electronic state. The lowest singlet electronic state is highly electrophilic, and therefore, evidence is provided by this study that explains the high photoreactivity of catBN. Furthermore, the reaction of borylnitrene catBN with ethene C2H4 was investigated under matrix isolation conditions both thermally and photochemically. In the thermal reaction (T = 35 K), the products of the reaction were assigned as aziridine and syn isomers of imine. Meanwhile, both the syn and anti isomers of imine were identified in the photoreaction in addition to aziridine.
Nitrene