Predicting Dinitrogen Activation by Carborane-Based Frustrated Lewis Pairs

Abstract

Activation of atmospherically abundant dinitrogen (N 2 ) under mild conditions has been a great challenge in chemistry for decades because of the significantly strong NN triple bond. The traditional strategy of N 2 activation was mainly limited to metallic species until the ground-breaking achievement of N 2 activation by two-coordinated borylenes was achieved experimentally in 2018. On the other hand, carborane derivatives have attracted considerable interest for small-molecule activation. Still, the utilization of carborane derivatives in N 2 activation remains elusive. Here, we design four types of carborane-based frustrated Lewis pairs (FLPs) to probe their potential for N 2 activation by systematical density functional theory calculations. Interestingly, all these carborane-based FLPs are found to become favorable both kinetically and thermodynamically for activating N 2 with low reaction barriers (ranging from 13.0 to 25.8 kcal mol −1 ) and high exothermicity, with ΔG values ranging from −37.5 to −51.0 kcal mol −1 , indicating a high potential for metal-free N 2 activation under mild conditions. Our study opens an avenue to metal-free N 2 activation, highlighting the great importance of carborane derivatives in the field of N 2 activation.

Predicting Small Molecule Activation including Catalytic Hydrogenation of Dinitrogen Promoted by a Dual Lewis Acid

“…Our group theoretically designed a series of FLPs that can be used for N 2 activation, such as NHC‐methyleneborane, [34] NHC‐borole, [35] and NHC‐borane, [36] in a thermodynamically and kinetically favorable manner. In addition, N 2 activation by five‐electron boron radicals, [37] carbene‐stabilized borylenes, [38] carborane‐based FLPs, [39] borenium, and borinium cations [40] have also been reported theoretically.…”

Recent progress in ammonia synthesis based on photoelectrocatalysis

“…Metal-free catalytic ammonia synthesis with high selectivity and ideal yield faces challenges until the breakthrough of N 2 activation based on the frustrated Lewis pairs (FLPs) in 2018. 81 FLPs with an electrophilic acid and nucleophilic base are favorable for the breaking of NuN through the electron transfer between the unoccupied orbitals of electrophilic acid and the nonbonding orbitals of nucleophilic base (Fig. 6a).…”

“…(d) Mechanism of over 10B/10Mo-C 3 N 4 in the photocatalytic N 2 fixation strategy,87 Copyright 2020, the Royal Society of Chemistry. (e) Gibbs energy over carborane-based FLPs for N 2 reduction 81. Copyright 2022, American Chemical Society.…”

Predicting dinitrogen activation by borenium and borinium cations

“…26,27 Furthermore, more FLPs, created by replacing the two-coordinated boron with borole 28 or borane, 29 have also been predicted to be efficient for activating N 2 both thermodynamically and kinetically, according to comprehensive DFT calculations. Additionally, five-electron boron-centered radicals, 30 carbene-stabilized borylenes 31 and carborane-based FLP 32 have also been investigated for N 2 activation. The introduction of cationic charge may boost the Lewis acidity of boron; hence, it poses the question of whether or not the activation of N 2 can be enhanced when the cationic boron replaces the neutral boron.…”