Evidence for a Unifying Ni^I/Ni^III Mechanism in Light-Mediated Cross-Coupling Catalysis

Area of Science:

• Organometallic Chemistry
• Photocatalysis
• Synthetic Organic Chemistry

Background:

• Nickel catalysis is crucial in synthetic chemistry, often involving paramagnetic nickel species.
• Oxidation state modulation of nickel via single-electron transfer is key to these reactions.
• Existing C(sp2)-heteroatom and C(sp2)-C(sp3) couplings rely on specific catalytic cycles and often require exogenous photoredox catalysts.

Purpose of the Study:

• To develop light-mediated nickel-catalyzed C(sp2)-C(sp3) bond formations without external photoredox catalysts.
• To expand the scope of C(sp2)-heteroatom couplings using photoactive ligands.
• To identify a photoactive nickel complex for efficient cross-coupling reactions.

Main Methods:

• Utilized a photoactive ligand in conjunction with a nickel catalyst.
• Investigated light-mediated cross-coupling reactions between aryl halides and benzyltrifluoroborate salts.
• Conducted mechanistic studies to elucidate the catalytic cycle.

Main Results:

• Demonstrated successful C(sp2)-C(sp3) bond formation using a photoactive ligand, obviating the need for exogenous photoredox catalysts.
• Identified a specific photoactive nickel complex that catalyzes cross-couplings between aryl halides and benzyltrifluoroborate salts.
• Provided mechanistic evidence for a Ni(I)/Ni(III) catalytic cycle involving transmetalation with organoboron compounds.

Conclusions:

• Photoactive ligands can enable light-mediated nickel catalysis, simplifying reaction setups.
• The developed nickel complex facilitates efficient C(sp2)-C(sp3) cross-coupling reactions.
• Understanding the Ni(I)/Ni(III) cycle is crucial for designing future catalytic systems.