Strategy used to synthesize high activity and low Pd catalyst for Suzuki coupling reaction: an experimental and theoretical investigation

Abstract

Unveiling the reaction mechanism is significant for developing high-performance catalysts. In this paper, a series of precisely controlled Pd_xM_147-x (M = Cu, Pt, Au, Rh, Ru) dendrimer encapsulated nanoparticles (DENs) has been successfully synthesized. The mechanisms of Pd_xM_147-x as catalysts for Suzuki cross-coupling reactions were investigated by combining experimental and theoretical methods. The experimental results indicate that Pd₇₄Cu₇₃ DEN shows similar activity to Pd₁₄₇ DEN and excellent substrate adaptability under mild reaction conditions. Moreover, the Cu component can play an important role in tuning the catalytic activity of Pd_xCu_147-x DEN. Density functional theory (DFT) calculations illustrate that the similar activities of the Pd₁₄₇ and Pd₇₄Cu₇₃ DENs originate from the comparable energy barriers of the rate-determining steps. The partial density of states (PDOS) and electron density differences demonstrate that Cu decreases the intensities of the valence orbitals of the top and edge Pd atoms and weakens orbital interactions between the intermediates and Pd₇₄Cu₇₃ DEN, leading to low desorption energies of the products. This work can provide a promising strategy to reduce the cost of Pd catalysts in Suzuki cross-coupling reactions.