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

Abstract

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.

Microflowers formed by complexation-driven self-assembly between palladium(ii) and bis-theophyllines: immortal catalyst for C–C cross-coupling reactions

“…So, we speculate that besides the roles of Cl − ion mentioned above, a suitable amount of chloride ion may be also helpful for reducing the reaction barrier on the oxidative addition. 50 This is still a question to be searched in the future.…”

Designing Zr12O12 nanocage for the delivery of anticancer drugs: a theoretical study

“…Moreover, this fact can be also confirmed by the average local ionization energy (ALIE) plot as shown in figure S4. It is observed that the local minima (marked with blue dots) of ALIE are always distributed on the O, S, and N atoms of drug molecules, further indicating that these sites are more susceptible to the electrophilic attack [50].…”

Suzuki–Miyaura Cross-Coupling Reaction Catalyzed by Al12M (M = Be, Al, C, and P) Superatoms with Different Numbers of Valence Electrons

“…In order to understand the in-depth nature of the oxidative addition of PhBr onto Al 12 M, the NPA charges on the Al 12 M units in the 1 M and 2 M * structures are illustrated in Figure S7. According to molecular orbital theory, 16,60 the electron pair from the bonding orbital of the C−Br bond is first donated to the empty hybrid orbital of metal atoms on the surface of Al 12 M, resulting in the negative charges on the Al 12 M units in 1 M during the initial adsorption of PhBr onto Al 12 M (see Figure S7). For Al 12 C and Al 12 P with 40 and 41 valence electrons, respectively, the acquisition of extra electrons from PhBr is detrimental to their stability in the resulting 1 M complexes, which leads to the higher relative free energies (ΔG) of 1 C and 1 P than those of 1 Be and 1 Al (see Figure 5).…”