Predicting Dinitrogen Activation by Boron Radical Cations

Activation
of dinitrogen (N2) under mild conditions
has been a particularly challenging project for decades, owing to
the highly strong NN triple bond. In recent years, the main
group species have emerged as a prominent strategy in the field of
dinitrogen activation, but the reported examples remain particularly
rare compared with transition metal complexes. Herein, we performed
a comprehensive density functional theory (DFT) calculation of N2 activation by boron radical cations. The calculations demonstrated
that N2 activation by boron radical cations was favorable
both kinetically and thermodynamically, with high exothermicity (ΔG value of −36.8 kcal/mol) and a low reaction barrier
(7.3 kcal/mol), indicating feasibility under mild conditions. Moreover,
principal interacting spin orbitals (PISOs) and intrinsic bond orbitals
(IBOs) analyses revealed that the boron radical cation activated N2 through two perpendicular interactions, including σ-type
donation and π-type backdonation. Additionally, further analysis
implied that π-type backdonation is essential for N2 activation. Our findings offer an alternative approach for metal-free
N2 activation, highlighting the significance of boron chemistry
in N2 activation.