title: Sonogashira couplings on the surface of montmorillonite-supported Pd/Cu nanoalloys.
abstract: To explore the true identity of palladium-catalyzed Sonogashira coupling reaction, montmorillonite (MMT)-supported transition metal nanoparticles (MMT@M, M=Pd, Cu, Fe, and Ni) were prepared, characterized, and evaluated systematically. Among all MMT@M catalysts, MMT@Pd/Cu showed the highest activity, and it was successfully extended to 20 examples with 57%-97% yields. The morphology characterization of MMT@Pd/Cu revealed that the crystalline bimetallic particles were dispersed on a MMT layer as nanoalloy with diameters ranged from 10 to 11 nm. In situ IR analysis using CO as molecular probe and XPS characterization found that the surface of Pd/Cu particles consisted of both catalytic active sites of Pd(0) and Cu(I). The experiments on the catalytic activities of MMT@M found that Pd/Cu catalyst system exhibited high activity only in nanoalloy form. Therefore, the Pd/Cu nanoalloy was identified as catalyst, on which the interatom Pd/Cu transmetalation between surfaces was proposed to be responsible for its synergistic activity.
authors.affiliation: Key Laboratory of Applied Surface and Colloid Chemistry MOE, School of Chemistry and Chemical Engineering, Shaanxi Normal University , Xi'an 710062, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Huaming
authors.initials: H
authors.lastname: Sun
authors.forename: Bo
authors.initials: B
authors.lastname: Yu
authors.forename: Guofang
authors.initials: G
authors.lastname: Zhang
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Zhang
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Gao
keywords: CO absorption; Sonogashira coupling; bimetallic catalysis; montmorillonite; nanoalloy