Oxidatively Induced Reductive Elimination: Exploring the Scope and Catalyst Systems with Ir, Rh, and Ru Complexes

Area of Science:

• Catalysis
• Organic Chemistry
• Organometallic Chemistry

Background:

• Direct C-H to C-C bond conversion is an attractive alternative to cross-coupling reactions.
• Reductive elimination is a crucial step in catalytic C-C bond formation, with efforts focused on its facilitation.
• Oxidation of metal centers in post-transmetalation intermediates presents a promising strategy to promote reductive elimination.

Purpose of the Study:

• To investigate the role of oxidatively induced reductive elimination (ORE) in C-C bond formation.
• To explore the substrate scope, catalyst systems, and oxidation methods for ORE.
• To demonstrate the broad applicability of ORE in metal-catalyzed C-H functionalization.

Main Methods:

• Utilized half-sandwich d6 Ir(III)-, Rh(III)-, and Ru(II)-aryl complexes.
• Employed chemical and electrochemical oxidation to generate post-transmetalation intermediates.
• Performed computational studies to analyze reductive elimination thermodynamics and activation barriers.
• Optimized catalytic conditions for Ir-, Rh-, and Ru-catalyzed C-C bond formation.

Main Results:

• Demonstrated that ORE plays a critical role in product-releasing C-C bond formation.
• Showcased ORE's broad operation with various Ir(III)-, Rh(III)-, and Ru(II)-aryl complexes.
• Confirmed that metal center oxidation facilitates reductive elimination even at ambient temperature.
• Observed significantly reduced activation barriers for reductive elimination upon increasing intermediate oxidation states.
• Successfully corroborated ORE in a Rh-methyl complex.

Conclusions:

• ORE is a viable and effective strategy for C-C bond formation via C-H functionalization.
• Oxidation of metal centers in post-transmetalation intermediates significantly lowers reductive elimination barriers.
• This mechanistic insight allows for the development of mild and efficient catalytic C-C bond formation reactions.