Rapid C-H bond activation by a monocopper(III)-hydroxide complex.

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Copper complexes are widely studied for their catalytic properties.
• Understanding the oxidation states and reactivity of copper is crucial for designing efficient catalysts.
• The generation and characterization of high-valent copper species remain an active area of research.

Purpose of the Study:

• To synthesize and characterize a novel copper(III)-hydroxide complex.
• To investigate the reactivity of this copper(III) intermediate in oxidation reactions.
• To elucidate the mechanism of hydrogen atom abstraction by the copper(III) complex.

Main Methods:

• One-electron oxidation of a tetragonal Cu(II) complex ([Bu(4)N][LCuOH]) at low temperature (-80 °C).
• Spectroscopic and theoretical analyses to confirm the formation and identity of the Cu(III) intermediate (LCuOH).
• Kinetic studies of the reaction with dihydroanthracene, including kinetic isotope effect measurements.

Main Results:

• The reactive intermediate LCuOH was successfully generated and identified as a Cu(III) complex.
• LCuOH reacted with dihydroanthracene to produce anthracene and a Cu(II) complex (LCu(OH(2))).
• Kinetic studies revealed a second-order rate law for H-atom abstraction with significant kinetic isotope effects (k(H)/k(D) = 44 at -70 °C).

Conclusions:

• A Cu(III)-OH moiety can function as a reactive species in oxidation reactions.
• The findings support the viability of Cu(III)-OH as a key intermediate in copper-catalyzed oxidation processes.
• This study provides insights into the fundamental reactivity of high-valent copper species.