Exploring N₂ activation using novel Lewis acid/base pairs: computational insight into frustrated Lewis pair...

Area of Science:

• Computational Chemistry
• Materials Science
• Catalysis

Background:

• Dinitrogen (N₂) activation is vital for synthesizing nitrogen compounds but challenging due to its strong triple bond.
• Current industrial N₂ conversion (Haber-Bosch process) is energy-intensive, relying on transition metal catalysts.
• Frustrated Lewis pairs (FLPs) offer a transition metal-free alternative for N₂ activation.

Purpose of the Study:

• Investigate N₂ activation by transition metal-free Lewis acids (LAs) and Lewis bases (LBs) using DFT.
• Determine the roles of LAs and LBs in N₂ capture and activation.
• Identify optimal LA-LB combinations for efficient N₂ activation.

Main Methods:

• Density Functional Theory (DFT) calculations to model N₂ interactions with LAs and LBs.
• Principal Component Analysis (PCA) to identify key factors governing LA electroaccepting power.
• Bonding analysis to characterize LA-N₂ and LB-N₂ interactions.

Main Results:

• LAs capture N₂, with efficiency linked to their electroaccepting characteristics (pyramidalization, orbital occupation, electrophilicity index).
• Triptycene-based LAs form the most stable N₂ complexes, but LBs are required for full N₂ triple bond activation via a 'push-pull' mechanism.
• LB nucleophilicity enhances activation; only three LA-LB combinations exhibit FLP characteristics, with triptycene-based LAs and tris-tert-butylphosphine being most promising.

Conclusions:

• LAs and LBs play distinct, complementary roles in transition metal-free N₂ activation.
• Triptycene-based systems are effective N₂-capturing agents.
• Optimized FLPs, particularly those involving triptycene-based LAs and tris-tert-butylphosphine, show significant potential for N₂ activation.