Intermolecular arene C-H activation by nickel(II)

Area of Science:

• Organometallic Chemistry
• Catalysis
• C-H Activation

Background:

• Intermolecular arene C-H activation is crucial for synthesizing complex organic molecules.
• Current methods often rely on expensive precious metals (4d and 5d) or harsh conditions.
• Developing cost-effective and mild catalytic systems remains a significant challenge.

Purpose of the Study:

• To investigate intermolecular arene C-H activation using divalent nickel species.
• To explore the reactivity of nickel complexes under extremely mild conditions.
• To assess the economic viability of nickel catalysts compared to alternatives.

Main Methods:

• Synthesis of nickel hydride complexes ([R-PNP]NiH) from Ni(COD)2 or [R-PNP]NiCl precursors.
• Reaction of [R-PNP]NiH with Lewis acids (B(C6F5)3) and alkylaluminum reagents (AlMe3) in arenes.
• Analysis of reaction products to determine activation pathways and catalytic efficiency.

Main Results:

• Efficient intermolecular arene C-H activation of benzene, toluene, and m-xylene was achieved using nickel(II) catalysts.
• Reactions proceeded under mild conditions (room temperature) with high yields.
• The study identified key intermediates and proposed reaction mechanisms involving zwitterionic species.

Conclusions:

• Divalent nickel complexes, particularly [R-PNP]NiH, are highly effective for intermolecular arene C-H activation.
• The developed nickel-based system offers a cost-effective and milder alternative to precious metal catalysts.
• The findings highlight the potential of inexpensive nickel catalysts in synthetic organic chemistry.