Air‐Stable and Highly Active Dendritic Phosphine Oxide‐ Stabilized Palladium Nanoparticles: Preparation, Characterization and Applications in the Carbon‐Carbon Bond Formation and Hydrogenation Reactions

Abstract

Dendrimer‐stabilized palladium nanoparticles were formed in the reduction of palldium bis(acetylacetonate) [Pd(acac)2] in the presence of phosphine dendrimer ligands using hydrogen in tetrahydrofuran. The resulting Pd nanoparticles were characterized by TEM, 31P NMR and 31P MAS NMR. The results indicated that the dendritic phosphine ligands were oxidized to phosphine oxides. These dendrimer‐stabilized Pd nanoparticles were demonstrated to be efficient catalysts for Suzuki and Stille coupling reactions and hydrogenations. The dendritic wedges served as a stabilizer for keeping the nanoparticles from aggregating, and as a vehicle for facilitating the separation and/or the recycling of the Pd catalyst. In the case of the Suzuki coupling reaction, these Pd nanoparticles exhibited high catalytic efficiency (TON up to 65,000) and air stability as compared with the commonly used homogeneous catalyst tetrakis(triphenylphosphine)palladium [Pd(PPh3)4]. In addition, the results obtained from the bulky dendritic substrate suggest that the Pd nanoparticles might act as reservoir of catalytically active species, and that the reaction is actually catalyzed by the soluble Pd(0) and/or Pd(II) species leached from the nanoparticle surface.

Long‐chain silanes as reducing agents part 1: a facile, efficient and selective route to amine and phosphine‐stabilized active Pd‐nanoparticles

“…All of the experiments were performed at room temperature (27)(28)(29)(30) • C) under a positive pressure of nitrogen. Solvents were purchased from EM science (Merck) and distilled prior to the use.…”

Highly efficient and recyclable water-soluble fullerene-supported PdCl2 nanocatalyst in Suzuki–Miyaura cross-coupling reaction

“…[30][31][32][33] and by using them, high yield can mostly be obtained. It has been veried that coordination bonding catalytic active substances with high surface energies and high surface-tovolume ratios can improve supported catalysts' efficiency.…”

Nanocatalysts for Hiyama, Stille, Kumada, and Negishi C–C Coupling Reactions

“…31 P NMR and 31 P magic angle spinning NMR results suggested that the phosphine ligands were oxidized to generate phosphine oxide species, but this did not affect their nanoparticle-stabilizing properties. 148 This system could efficiently catalyze the Stille coupling reaction in a DMF/water medium, in the presence of cesium fluoride as an additive. Yields were high, and it was noted that these catalytic systems were much more efficient than the Pd(PPh 3 ) 4 complexes commonly used in Stille couplings.…”