Computational Comparative Mechanistic Study of C-E (E=C,N,O,S) Coupling Reactions through CO₂ Activation Mediated by...

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Catalysis

Background:

• Uranium complexes offer unique reactivity for small molecule activation.
• Functionalization of carbon dioxide (CO2) is crucial for sustainable chemistry.
• Trivalent uranium complexes provide a platform for exploring novel catalytic pathways.

Purpose of the Study:

• To investigate the DFT mechanism of CO2 functionalization by trivalent uranium complexes.
• To understand the factors governing the reactivity and selectivity of these complexes.
• To explore the formation of C-C, C-N, C-S, and C-O bonds using uranium catalysis.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Mechanistic studies focused on CO2 insertion into U-E bonds.
• Analysis of free energy barriers and reaction intermediates was performed.

Main Results:

• A two-step mechanism involving CO2 insertion and carboxylate reorientation was identified.
• Free energy barriers varied significantly based on the U-E bond and R group.
• Reactivity order was determined as Cpda-S < Cpda-CC < Cpda-CSi < Cpda-N < Cpda-O.
• Silylation of the insertion product was studied, favoring a backside attack mechanism.

Conclusions:

• The reactivity of trivalent uranium complexes in CO2 functionalization is dictated by U-E bond strength and R group nucleophilicity.
• DFT provides valuable insights into the mechanistic pathways and energetic profiles.
• These findings contribute to the development of novel uranium-based catalysts for CO2 utilization.