Hydrosoluble Betaine-Stabilized CuRu Bimetallic Nanoparticles for the Aqueous Semi-Hydrogenation of Alkynols

Abstract The selective semi-hydrogenation of alkynols to alkenols is an important catalytic transformation, since they serve as intermediates in the production of fine chemicals, including vitamins, pharmaceuticals, agrochemicals, fragrances, and flavors. In this work, we have synthesized colloidal CuxRuy@WS-L nanoparticles (where x, y = 0, 1, and 2) stabilized by a betaine adduct containing hydrophilic sulfonate groups (water-soluble ligand, WS-L), which improves their dispersibility in aqueous media as demonstrated by DLS analysis. Metal CuRu alloying was confirmed by EDX line-scan analysis and XPS/XAS spectroscopies, while IR and XPS spectroscopies and solid-state NMR demonstrated the effective coordination of the WS-L onto the nanoparticle surface. The catalytic performance of CuxRuy@WS-L was evaluated in the semi-hydrogenation of 2-butyne-1,4-diol in water. Among the different metal compositions investigated, Cu1Ru1@WS-L emerged as the most promising catalyst due to its optimal balance between activity and selectivity toward the corresponding alkene. While Cu (Cu@WS-L) and Cu-rich nanoparticles (Cu2Ru1@WS-L) showed low activity, Ru (Ru@WS-L) and Ru-rich nanoparticles (Cu1Ru2@WS-L) led to increased over-hydrogenation. Finally, the versatility of the Cu1Ru1@WS-L was evaluated by expanding the reaction scope to various internal and terminal hydroxy alkynes, all of which were efficiently converted with high selectivity to the corresponding alkenes.