Atomically Dispersed Palladium Promoted Suzuki-Miyaura Cross Coupling

Area of Science:

• Organic Chemistry
• Materials Science
• Catalysis

Background:

• The Suzuki-Miyaura cross-coupling reaction is a cornerstone of modern organic synthesis for forming carbon-carbon bonds.
• Developing efficient, stable, and recyclable catalysts is crucial for sustainable chemical synthesis.
• Palladium catalysts are widely used but can be expensive and prone to aggregation.

Purpose of the Study:

• To report a novel isolated palladium catalyst supported on polymeric carbon nitride (Pd/PCN).
• To investigate the efficiency of the Pd/PCN catalyst in Suzuki-Miyaura cross-coupling reactions at room temperature.
• To explore the effect of palladium species size and reaction atmosphere on catalytic performance.

Main Methods:

• Synthesis of palladium catalyst supported on polymeric carbon nitride (Pd/PCN).
• Suzuki-Miyaura cross-coupling reaction of bromobenzene and phenylboronic acid.
• Characterization of catalyst activity, including mole-specific activity and effect of Pd size (isolated species vs. nanoparticles).
• Continuous flow tests to evaluate catalyst stability and performance under different atmospheres (O2 vs. Ar).
• In-situ infrared spectroscopy for mechanistic investigations.

Main Results:

• The Pd/PCN catalyst demonstrated efficient Suzuki-Miyaura cross-coupling of bromobenzene and phenylboronic acid at room temperature.
• A 2 wt% Pd loading on the Pd/PCN catalyst achieved the highest mole-specific activity.
• Isolated palladium species exhibited higher catalytic activity compared to palladium nanoparticles.
• Catalyst performance was sensitive to the reaction atmosphere, with increased side reactions (self-coupling) under O2 flow.
• Mechanistic studies revealed the role of K2CO3 in activating phenylboronic acid.

Conclusions:

• Isolated palladium species supported on polymeric carbon nitride represent a highly active catalyst for Suzuki-Miyaura cross-coupling.
• The catalyst offers an efficient route for carbon-carbon bond formation under mild, room-temperature conditions.
• Understanding the influence of reaction atmosphere and catalyst morphology is key to optimizing cross-coupling reactions.