Theoretical study on ligand conformational self-adaptation for modulating reactivity.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Palladium (Pd) catalysts with Josiphos-type ligands are crucial for efficient catalytic processes.
• Understanding reaction mechanisms is key to optimizing selectivity and reactivity.

Purpose of the Study:

• To elucidate the reaction mechanisms and dynamic conformational changes in Pd-catalyzed bicyclization/carbonylation of 1,6-enynes.
• To investigate the role of Josiphos-Pd ligand conformations in reactivity and enantioselectivity.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Analysis of reaction pathways, including migratory insertion.
• Surface distance projection maps and Intermolecular Geometry (IGM) analysis.

Main Results:

• The most favorable pathway involves an unusual alkene insertion into the carbon-palladium bond.
• Josiphos-Pd backbone self-adaptation allows two distinct ligand conformations, enhancing reactivity.
• A half-chair conformation is preferred for migratory insertion, controlling rate and enantioselectivity.
• Steric interactions between the ligand and substrate are critical for enantioselectivity.

Conclusions:

• DFT calculations provide mechanistic insights into Pd-catalyzed bicyclization/carbonylation.
• Ligand conformation and substrate-ligand steric effects are vital for achieving high enantioselectivity.
• The study highlights the importance of catalyst design and computational methods in developing selective catalytic processes.