Size-Dependent Catalytic Activity and Fate of Palladium Nanoparticles in Suzuki–Miyaura Coupling Reactions

Abstract

Stable, catalytically active palladium nanoparticles of various average diameters (1.9–7.4 nm) have been synthesized and characterized by X-ray diffraction, spectroscopy, and microscopy techniques to demonstrate remarkable size-dependent and renewed catalytic activity toward the Suzuki–Miyaura coupling reaction in green protocol. The catalytic activity is found to depend on the amount of the reducing agent, stabilizer–precursor ratio, solvent composition, and aryl halides used. The product obtained by this reaction is characterized by 1 H NMR, 13 C NMR, and IR spectroscopy analyses. A newly developed kinetic equation illustrates that while the catalyst particles of the lowest dimension are gradually exposed to the reactants and hence activated due to partial removal of capping polymer from the catalyst surface, others are deactivated due to agglomeration during the progress of the reaction, as conformed by the microscopic profiles of the used and unused catalysts.

Regulating the Catalytic Activity of Pd Nanoparticles by Confinement in Ordered Mesoporous Supports

“…ICP‐OES analysis of the spent catalysts indicated there was no Pd leaching. Suzuki couplings using colloidal suspensions of PVP or PVA capped Pd nanoparticles have shown similar results: very small variations in the 3 to 5.2 nm regime, but a dramatic enhancement when particle size reaches 1.9 nm [5b,20] . This result has been attributed to the increasing proportion of edges and vertices with decreasing nanoparticle size [20] .…”

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

“…The copper nanoparticle size was 18 ± 2 nm, and it was determined by TEM, as well as quasi-elastic light scattering data (QELS). It should be expressed that the size of the nanoparticle profoundly affect the catalytic cross-coupling reactions [32]. Unfortunately, these copper nanoparticles did not performed well in the reusability experiment.…”

Amphiphilic PdII‐NHC Complexes on 1,3‐Alternate p‐tert‐Butylthiacalix[4]arene Platform: Synthesis and Catalytic Activities in Coupling and Hydrogenation Reactions

“…It is noteworthy that similar catalytic systems made in situ from 3 or 4 and Pd(OAc) 2 (Table , entries 3,4) were found to be not so effective as corresponding complexes 13 or 14 , however, turned out to be better than “pure” Pd(OAc) 2 (Table , entry 5). Incomplete in situ complex formation of 3 or 4 and Pd(OAc) 2 may be a reason of lower activity of catalytic systems obtained in situ: partially unreacted Pd(OAc) 2 forms Pd‐black, which is usually less catalytically active than small metal NPs , . Indeed, according to microphotography of mixture of 4 with Pd(OAc) 2 , treated by NaBH 4 (see Supp.…”