Atomically Dispersed Palladium Promoted Suzuki-Miyaura Cross Coupling.

The palladium-catalyzed Suzuki-Miyaura cross coupling reaction to forge carbon-carbon bonds fundamentally changes the practice of organic synthesis. Herein an isolated palladium catalyst supported on polymeric carbon nitride (Pd/PCN) for efficient cross coupling of bromobenzene and phenylboronic acid at room temperature is reported. It is demonstrated that the Pd/PCN catalyst with a 2 wt% Pd loading achieves the highest mole-specific activity. In addition, the size of supported Pd can strongly affect the reaction performance: the isolated Pd species exhibit higher activity compared to the Pd nanoparticles. The continuous flow tests demonstrate that the catalytic properties of the Pd/PCN catalyst strongly depend on the reaction atmosphere: Pd-catalyzed self-coupling of phenylboronic acid as a side reaction is more pronounced under an O₂ flow than in an Ar flow. Detailed mechanistic investigations through in situ infrared spectroscopy reveal the role of the base K₂CO₃ in activating the phenylboronic acid.