Predicting Small Molecule Activations Including Dinitrogen Based on an Inorganic Benzene B₄N₂ Framework.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Catalysis

Background:

• Dinitrogen (N₂) activation is crucial for synthesizing nitrogen-containing compounds but remains challenging, especially for main group elements.
• Transition metal complexes dominate N₂ activation research, with fewer examples involving main group species.

Purpose of the Study:

• To explore a new [4 + 2] cycloaddition pathway for N₂ activation initiated by an inorganic benzene.
• To investigate the electronic and energetic factors governing this N₂ activation process.
• To assess the potential of the inorganic benzene for activating other small molecules.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model the reaction mechanism.
• Analysis of key parameters including activation energy, bond distances (dNN), vibrational frequencies (νNN), and Wiberg bond indices (WBINN) were used to characterize N₂ activation.
• Computational modeling of reactions with other small molecules like CO₂, acetylene, and ethylene.

Main Results:

• A [4 + 2] cycloaddition reaction of N₂ was successfully demonstrated with a low activation energy of 12.5 kcal mol⁻¹.
• N₂ activation was confirmed by significant elongation of the N-N bond, reduced vibrational frequency, and weakened Wiberg bond index.
• The introduction of a Lewis acid (HB(C₆F₅)₂) enhanced product stability via a "push-pull" electronic effect.
• The inorganic benzene also showed efficient activation of CO₂, acetylene, ethylene, and acetonitrile with low reaction barriers (4.7–11.6 kcal mol⁻¹).

Conclusions:

• This work presents a viable and computationally validated alternative approach for N₂ activation and functionalization using main group inorganic benzene.
• The findings support the feasibility of employing a dual Lewis acid strategy for effective dinitrogen activation.
• The demonstrated inorganic benzene platform shows broad potential for activating various small molecules.