Cross-Coupling through Ag(I)/Ag(III) Redox Manifold

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Silver (Ag) is often used as an additive in metal-catalyzed cross-coupling reactions.
• Its role as a catalytically active species, particularly in redox processes, is frequently overlooked.
• Misconceptions about silver's inability to undergo 2e- redox steps limit its exploration in catalysis.

Purpose of the Study:

• To provide definitive proof of silver's capability in redox catalysis.
• To investigate the Ag(I)/Ag(III) redox cycle for the oxidative trifluoromethylation of arenes.
• To challenge the prevailing view of silver's limited role in cross-coupling reactions.

Main Methods:

• Demonstration of facile Ag(I)/Ag(III) 2e- oxidation mediated by air.
• Characterization of novel organosilver(III) compounds.
• Utilizing silver(III) intermediates for cross-coupling reactions.

Main Results:

• Established the elementary steps for Ag(I)/Ag(III) redox catalysis in arene trifluoromethylation.
• Synthesized and fully characterized key organosilver(III) intermediates, including [K]+[Ag(III)(CF3)4]- (K-1), [(bpy)Ag(III)(CF3)3] (2), and [(phen)Ag(III)(CF3)3] (3).
• Showcased the utility of compound 3 in cross-coupling, enabling the trifluoromethylation of diverse arylboron compounds via [Ag(III)(aryl)(CF3)3]- intermediates.

Conclusions:

• Silver actively participates in redox catalysis, specifically in trifluoromethylation reactions.
• The study provides concrete evidence for silver's catalytic competence in cross-coupling, utilizing a Ag(I)/Ag(III) redox mechanism.
• This research overturns long-held assumptions about silver's limitations in undergoing cross-coupling reactions independently.