Electronic bond tuning with heterocyclic carbenes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Heterocyclic carbenes (HCS) are versatile ligands in organometallic chemistry.
• Understanding ligand effects is crucial for designing efficient catalytic systems.
• The impact of P-heterocyclic carbenes (PHCs) versus N-heterocyclic carbenes (NHCs) on catalytic intermediates requires detailed investigation.

Purpose of the Study:

• To investigate the influence of the heterocyclic carbene (HC) ring's nature on the stability of key intermediates in ruthenium (Ru), palladium (Pd), and gold (Au) catalyzed reactions.
• To compare the effects of P-heterocyclic carbenes (PHCs) and N-heterocyclic carbenes (NHCs) as ligands.
• To rationalize the observed effects using energy decomposition analysis.

Main Methods:

• Computational modeling of catalytic intermediates.
• Energy Decomposition Analysis (EDA) to quantify bonding interactions.
• Focus on Ru-promoted olefin metathesis, Pd cross-coupling, and Au-catalyzed reactions.

Main Results:

• PHCs increase the bonding of labile ligands and substrates in Ru-catalyzed olefin metathesis, with minimal effect on the ruthenacycle intermediate.
• PHC dissociation is favored over NHC dissociation in Pd cross-coupling reactions.
• PHCs weaken the Au-OH bond in Au-catalyzed reactions.

Conclusions:

• The electronic and steric properties of the HC ligand significantly modulate the stability of intermediates in various metal-catalyzed transformations.
• PHCs offer distinct reactivity profiles compared to NHCs, impacting ligand lability and substrate/metal interactions.
• Computational insights provide a foundation for the rational design of HC ligands for specific catalytic applications.