Disassembling Metal Nanocrystallites into Sub‐nanometric Clusters and Low‐faceted Nanoparticles for Multisite Catalytic Reactions

Abstract

Metal nanocrystallites present saturated atoms, in planes, and unsaturated metal atoms, in corners and vertices, for catalytic applications. However, both sites are spatially complementary and simultaneously excluding for a given particle, thus their number cannot be independently maximized for a catalytic process. Here, it is shown that the independent dosage of Au clusters and metallic Au nanoparticles dramatically improves the catalytic activity of Au for the Sonogashira reaction, enabling the coupling of a wide range of iodo‐, bromo‐, and activated chloro‐derivatives with aromatic and aliphatic alkynes, and outperforming ligand‐free Pd and Cu catalysts. Mechanistic studies reveal that the unsaturated atoms of the cluster activate the alkyne and that the saturated atoms of the metallic nanoparticle preferentially activate the halide, to finally perform the coupling. Thus, a precise combination of sub‐nanometric metal clusters and metal nanoparticles, together, constitute a new catalytic strategy to substitute metal nanocrystallites in reactions in which both unsaturated and saturated atoms play a key role.

Base-Controlled Heck, Suzuki, and Sonogashira Reactions Catalyzed by Ligand-Free Platinum or Palladium Single Atom and Sub-Nanometer Clusters

“…To further confirm that sub-nanometer Pt species are the catalytically active species and that the EVOH polymer does not dissolve nor interfere during the reaction, the Heck reaction catalyzed either by PtCl 2 or Pt@EVOH was also monitored by NMR and Fourier transform infrared (FT-IR) spectroscopy (Figures S12–S13). In the NMR experiments, deuterated DMF was used as solvent, and 4-fluoroiodobenzene was chosen as a substrate to follow the reaction not only by 1 H but also by 19 F NMR spectroscopy.…”

“…Aryl bromides are also reactive and produce the same products, but with lower yields. It must be noted that EVOH and Au@EVOH cannot perform the Heck coupling at all with any haloarene, in contrast to Pt@EVOH, and that the reaction yields of the desired products are also dependent on the type of substituents, even though the oxidative addition is not the only RDS.…”

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles

“…Taking into consideration that different molecules may be activated on different types of Au species, the combination of metal clusters and nanoparticles has been shown to enhance the activity of either cluster or nanoparticles for the Sonagashira reaction. 541 Following that idea, in a recent work, it has been demonstrated that the combination of Au nanoparticles and clusters shows significantly higher activity than a single type of catalyst for Sonogashira reaction. As described in Figure 107 , supported Au clusters can leach into solution and activate the C–H bond terminal alkynes with the help of base.…”

“… Mechanistic proposal for the Sonogashira coupling with Au clusters and Au Nanoparticles as bifunctional catalyst. Adapted with permission from ref ( 541 ). Copyright 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

“…As we have discussed before, the catalytic behavior of metal clusters is distinct from that of metal nanoparticles. Taking into consideration that different molecules may be activated on different types of Au species, the combination of metal clusters and nanoparticles has been shown to enhance the activity of either cluster or nanoparticles for the Sonagashira reaction . Following that idea, in a recent work, it has been demonstrated that the combination of Au nanoparticles and clusters shows significantly higher activity than a single type of catalyst for Sonogashira reaction.…”