Transmetalation Reactions Triggered by Electron Transfer between Organocopper Complexes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Copper complexes, such as [Cu(bipy)(C₆F₅)], are known catalysts for cross-coupling reactions.
• The reactivity of these complexes can be influenced by the nature of the aryl iodide coupling partner.

Purpose of the Study:

• To investigate the reaction mechanism of [Cu(bipy)(C₆F₅)] with aryl iodides, particularly focusing on the formation of homocoupling products.
• To elucidate the role of specific fluorinated aryl iodides in altering the reaction pathway.

Main Methods:

• Kinetic studies were employed to analyze the reaction rates and identify mechanistic steps.
• Density functional theory (DFT) calculations were utilized to model the electronic interactions and transition states.

Main Results:

• While most aryl iodides yield heterobiphenyls via cross-coupling, the use of a specific fluorinated aryl iodide (Rf-I) resulted in the formation of homocoupling products.
• Kinetic data suggest a mechanism for homocoupling involving transmetalation from Cu(I) to Cu(III) intermediates.
• DFT calculations revealed a Cu(I)-Cu(III) electron transfer coupled with iodine bridging, followed by transmetalation within a triplet-state dimer of Cu(II) units.

Conclusions:

• The study uncovers a unique reaction pathway for copper-catalyzed coupling reactions when using sterically hindered and electron-deficient aryl iodides.
• A novel mechanism involving Cu(I)-Cu(III) interactions and transmetalation in a dimeric Cu(II) species is proposed for homocoupling.
• This research provides deeper insights into the intricate mechanisms of copper-catalyzed cross-coupling and homocoupling reactions.