Carbon-Carbon Cross-Coupling Reactions

Luo, Zundu

doi:10.1007/978-981-15-9704-6_9

Cited by 1 publication

(1 citation statement)

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“…Diverse materials employed as catalysts include metal oxides, metal complexes, and organic and inorganic polymers, as well as biocatalysts and photocatalysts. − Because of the metastability of free clusters, such reactions are usually catalyzed by clusters on inert supports or by ligated clusters. − The ligand protects the cluster core, whereas the surface reduces mobility and inhibits coalescence. Within the list of the notable chemical reactions where metal clusters are frequently used as a catalyst, the C–C cross-coupling reaction deserves a noteworthy mention. − Here, two organic fragments are combined together using a suitable catalyst. , One of the most important catalysts for such reactions is palladium clusters/nanoparticles. The reactions are usually carried out under homogeneous conditions, utilizing ligands to enhance activity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

Developing Efficient Suzuki Cross-Coupling Catalysts by Doping Palladium Clusters with Silver

Sengupta

Bista

2021

ACS Catal.

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It is shown that doping of a Pd cluster by Ag atoms can provide an efficient catalyst for the Suzuki–Miyaura cross-coupling reactions. We demonstrate this intriguing possibility by considering a model reaction involving bromobenzene and phenylboronic acid as reagents where the reaction involves oxidation, transmetallation, and reduction steps. We have examined the reaction barriers of all three steps for a conventional ligated Pd catalyst, a nearly icosahedral Pd13 cluster, and a monosilver-doped Pd12Ag cluster using gradient-corrected density functional theory. It is observed that the reaction carried out on the Pd sites adjacent to an Ag atom in a Pd12Ag cluster shows substantially lower barriers for the oxidation and reduction steps compared to the conventional ligated Pd catalyst and the pure Pd13 cluster. A detailed analysis indicates that the Ag site donates charge to the neighboring Pd site. While such a donation may have been expected to reduce the barrier for the oxidative step, the lowering of the barrier for the reduction step indicates that the respective sites not only act as a donor but can also serve as an acceptor for the reduction step. Furthermore, because of the differential donor–acceptor characteristic of the Ag and Pd atoms, it is observed that the barrier heights of the redox steps are primarily dependent on the chosen active site. The calculated results show that by altering the atom (Ag or Pd) at the active site of the reaction, the activation energies of the redox steps can either be reduced or increased. This shows that the active sites of a bimetallic cluster-like Pd12Ag can be utilized to control the barrier heights of suitable chemical reactions. The relative trend of the barrier heights for both clusters is also observed to be predictable by the conceptual density functional theory. Previous studies in our group have indicated that the reaction barriers for Pd n clusters can be lowered by supporting them on reduced graphene. We, therefore, propose that silver-doped Pd n clusters may provide an even better catalyst.

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