Phosphinine-Based Ligands in Gold-Catalyzed Reactions

Area of Science:

• Organometallic Chemistry
• Homogeneous Catalysis
• Ligand Design

Background:

• Phosphorus(III) compounds are crucial ligands in homogeneous catalysis.
• Developing novel ligands with tunable steric and electronic properties is essential for advancing catalytic efficiency.
• Existing cationic phosphorus-based gold catalysts offer good performance but exploring neutral alternatives is of interest.

Purpose of the Study:

• To synthesize and characterize novel phosphorus-based ligands: phosphinines, 1-phosphabarrelenes, and 5-phosphasemibullvalenes.
• To evaluate the steric and electronic properties of these new ligands.
• To assess their performance as ligands in gold(I)-catalyzed reactions.

Main Methods:

• Synthesis of substituted phosphinines, 1-phosphabarrelenes, and 5-phosphasemibullvalenes.
• Calculation of steric parameters (buried volume, %V_bur).
• Determination of electronic parameters (Tolman electronic parameter) via [LNi(CO)₃] complexes.
• Extended-Transition-State Natural Orbital for Chemical Valence (ETS-NOCV) calculations for σ- and π-interactions in [LAuCl] complexes.
• X-ray diffraction analysis of Au(I) coordination compounds.
• Application in gold(I)-catalyzed cycloisomerization of N-2-propyn-1-ylbenzamide.

Main Results:

• Successful synthesis and characterization of three classes of P(III) ligands.
• Quantification of steric and electronic properties, providing insights into ligand behavior.
• Demonstration of high catalytic activity and selectivity in gold(I)-catalyzed cycloisomerization reactions.
• Performance comparable to established cationic phosphorus-based gold catalysts.

Conclusions:

• The synthesized phosphinines, 1-phosphabarrelenes, and 5-phosphasemibullvalenes are effective ligands for gold(I) catalysis.
• These neutral P(III) ligands offer a viable alternative to cationic systems, exhibiting excellent catalytic outcomes.
• The study provides a comprehensive evaluation of novel ligand structures for homogeneous catalysis.