Au Core–Pd Shell Bimetallic Nanoparticles Immobilized within Hyper-Cross-Linked Polystyrene for Mechanistic Study of Suzuki Cross-Coupling: Homogeneous or Heterogeneous Catalysis?

Abstract

The synthesis of catalytically active bimetallic Au–Pd nanoparticles stabilized in hyper-cross-linked polystyrene (HPS) for Suzuki cross-coupling of 4-bromoanisole (4-BrAn) and phenylboronic acid is presented. The core–shell structure with a thin (less than 1 nm) Pd shell and a Au core was proven by X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. More than a 2-fold increase in 4-BrAn conversion was found in comparison with monometallic Pd/HPS. Moreover, when the Suzuki reaction was carried out under visible-light irradiation, the product yield further increased by about 1.3 times (from 56.1% up to 73.7%). This effect was assigned to a local surface plasmon resonance arising in the Au core that allowed electron transfer to the extremely thin Pd layer due to intimate contact with gold. The results suggest that the rate-limiting step of the catalytic cycle takes place on the surface of the Pd shell, serving as evidence of the heterogeneous catalysis nature.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…Under visible-light irradiation, the photogenerated electrons and holes activate the chloroarene and aryl boronic acid coupling partners, respectively.T he CeO 2 nanoporousm aterial enhances the photoabsorption and chargec arrierg eneration in Au. [416] It should be noted that all heterogeneousp hotocatalysts we discussed here requiret he presence of Pd for accelerating the reaction. [415] By replacing the TiO 2 support with ah yper-cross-linked polystyrene (HPS) material, Kiwi-Minsker et al carriedo ut the light-mediated crosscoupling of bromoarenesa nd aryl boronic acids in the presence of an Au/Pd/HPSp hotocatalyst.…”

Engineering of highly active Au/Pd supported on hydrogenated urchin-like yolk@shell TiO2 for visible light photocatalytic Suzuki coupling

“…12,23,24 With the help of the strong localized surface plasmon resonance (LSPR) of Au under light irradiation, Au/Pd bimetallic nanoparticles have been proven to be efficient in light harvesting and as catalysts for the Suzuki coupling reaction. [25][26][27] In this regard, several efforts have been devoted to improvement of the activity of heterogeneous AuPdbased TiO 2 catalysts for the visible-light-induced Suzuki coupling reaction. Yan et al reported a well-designed Au-TiO x -Pd photocatalyst that exhibited high performance towards Suzuki-Miyaura reactions under ambient conditions under solar irradiation.…”

Structure controlled Au@Pd NPs/rGO as robust heterogeneous catalyst for Suzuki coupling in biowaste‐derived water extract of pomegranate ash

“…[ 1,13–16 ] These are afflicted by the loss of activity ascribed to Pd leaching, low reactivity, narrow substrate scope, thermal sensitivity, agglomerate formation, and demand of high temperature and additional base. [ 1,13–19 ] The decrease of Pd by leaching can be attributed by a complex mechanism including pure homogeneous or heterogeneous or both, [ 19–23 ] and the mechanism was systematically illustrated in earlier work. [ 19 ] In the catalytic processes of Suzuki coupling, oxidative addition of aryl halide to Pd 0 NPs generates a Pd II complex, which engages in transmetallation with arylboronic acids (ABAs) to form a diaryl Pd II complex with high probability to be in soluble form.…”

“…[ 1,13–19 ] The decrease of Pd by leaching can be attributed by a complex mechanism including pure homogeneous or heterogeneous or both, [ 19–23 ] and the mechanism was systematically illustrated in earlier work. [ 19 ] In the catalytic processes of Suzuki coupling, oxidative addition of aryl halide to Pd 0 NPs generates a Pd II complex, which engages in transmetallation with arylboronic acids (ABAs) to form a diaryl Pd II complex with high probability to be in soluble form. The regenerated Pd 0 particles from diaryl Pd II in the final reduction step may be recaptured onto the surface of existing Pd NPs or remain in solution.…”