C-N Bond Formation at Discrete Cu^III-Aryl Complexes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Chemistry

Background:

• Copper(III) aryl species are crucial but poorly understood intermediates in copper-catalyzed bond formations.
• The rarity of discrete Cu(III)-Ar complexes hinders mechanistic studies of C-heteroatom bond formation and byproduct generation (Ar-H, Ar-Ar).

Purpose of the Study:

• To synthesize and characterize novel copper(II) and copper(III) aryl complexes.
• To investigate the reactivity of these complexes in C-N coupling reactions.
• To elucidate the mechanisms of byproduct formation in copper-catalyzed reactions.

Main Methods:

• Synthesis of copper(II) aryl complexes ([TBA][LCuII-ArR]) using various aryl donors (ZnAr2R, TMS-ArR, ArRBpin).
• Oxidation of copper(II) complexes to generate copper(III) aryl complexes (LCuIII-ArR).
• Reaction of copper(III) complexes with nitrogen nucleophiles, followed by Hammett analysis.

Main Results:

• Successful synthesis of a series of Cu(II) and Cu(III) aryl complexes mimicking reaction intermediates.
• C-N coupling products obtained in up to 64% yield, alongside Ar-H and Ar-Ar byproducts.
• Hammett analysis (ρ = -1.66) indicates electrophilic character of LCuIII-ArR, supporting proposed reaction mechanisms.

Conclusions:

• The study provides the first discrete Cu(III)-aryl complexes relevant to C-N coupling.
• Mechanisms for the formation of Ar-H and Ar-Ar byproducts in copper-catalyzed coupling reactions are proposed.
• The findings offer critical insights into the mechanistic aspects of copper-catalyzed C-heteroatom bond formation.