Palladium on carbon nanoparticles (Pd/C) have long been used as an effective heterogeneous catalyst for cross-coupling reactions, such as the Suzuki reaction and Buchwald-Hartwig reaction. Heterogenous catalysts are attractive options for industrial-scale reactions as the expensive catalyst can be easily removed from the reaction and reused. However, palladium nanoparticles have been shown to leach palladium atoms off of the nanoparticle surface. Once dissociated in solution it becomes more difficult to remove the palladium upon completion of the reaction, leading to product contamination. Palladium leaching also limits the reuse of the catalyst, ultimately resulting in higher costs and harmful environmental effects. We sought to find a more affordable and environmentally friendly replacement for the classic palladium nanoparticle catalyst by alloying the palladium with nonmetals, in particular palladium phosphide on carbon (PdP<sub>x</sub>/C) and palladium boride on carbon (PdB<sub>x</sub>/C). The alloying of palladium with phosphorous and boron alters the electronic properties of the palladium and may prevent palladium leaching. We will present our results using small-scale screening and analysis via gas-chromatography-mass spectrometry (GC-MS) to compare these two catalysts to commercially purchased palladium on carbon in the Suzuki reaction. Additionally, we have looked at eliminating the need for palladium entirely by alloying copper with nonmetals, with positive preliminary results observed in cross-coupling reaction screening.

Identification of economical cross-coupling catalysts by small scale reaction screening with gas chromatography-mass spectrometry

ACS Spring 2022

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