Rationalizing the influence of α-cationic phospholes on π-catalysis

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Catalysis Research

Background:

• Gold(I)-catalysts are known for high activity in various organic transformations.
• Ligand design is crucial for tuning catalyst performance and reaction outcomes.
• Phosphine ligands are commonly used, but novel ligand scaffolds are of interest.

Purpose of the Study:

• To computationally investigate the physical factors responsible for the enhanced activity of gold(I)-catalysts featuring α-cationic phosphole ligands.
• To elucidate the mechanism by which cationic phosphole ligands influence the catalytic cycle in hydroarylation reactions.

Main Methods:

• Quantitative analysis using the Activation Strain Model (ASM) of reactivity.
• Energy Decomposition Analysis (EDA) was employed to dissect interaction energies.
• Computational modeling of gold(I)-catalyzed hydroarylation reactions involving phenylacetylene and mesitylene with various phosphole and phosphine ligands.

Main Results:

• Cationic phosphole ligands induce significant geometric and electronic structure changes in the intermediate π-complex.
• The electrophilicity of the gold-acetylene complex is substantially enhanced by cationic phosphole ligands.
• A key π(mesitylene) → π*(LAu-acetylene complex) molecular orbital interaction is strengthened, correlating with increased catalytic activity.

Conclusions:

• The enhanced electrophilicity of the π-complex, driven by cationic phosphole ligands, is the primary factor for the observed high catalytic activity.
• The study provides fundamental insights into the electronic effects of cationic phosphole ligands in gold catalysis.
• Computational methods like ASM and EDA are effective tools for understanding reactivity in catalytic systems.