π-Complexation in nickel-catalyzed cross-coupling reactions.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Reaction Mechanisms

Background:

• Oxidative addition is a key step in many catalytic cycles.
• Understanding the initial steps is crucial for catalyst design.
• Nickel catalysts are versatile in organic synthesis.

Purpose of the Study:

• To determine the rate-limiting step in the oxidative addition of zerovalent nickel to haloarene substrates.
• To investigate the role of π-complexation in the reaction mechanism.
• To elucidate the mechanism using experimental and computational methods.

Main Methods:

• Experimental kinetic isotope effect (KIE) studies.
• Density functional theory (DFT) computations.
• Analysis of haloarene substrates including o-methylbenzene, dimethoxybenzene, and thiophene derivatives.

Main Results:

• The kinetic isotope effect (KIE) indicates that the first irreversible step is π-complexation.
• DFT calculations confirm the stability of η(2)-bound π-complexes.
• Ring-walking of the Ni(0) catalyst and subsequent oxidative addition are predicted to be facile.

Conclusions:

• The study experimentally and computationally confirms π-complexation as the initial irreversible step in the oxidative addition of Ni(0) to haloarenes.
• The findings provide insights into the mechanism of nickel-catalyzed C-X bond activation.
• This work contributes to the development of more efficient catalytic systems.