In the present study, we optimize the yolk–shell nanostructure in a palladium–silica system for the purpose of attaining high activity in Suzuki cross-coupling reactions. Pd@porous SiO2 (Pd@pSiO2) yolk–shell nanoparticles, bearing tiny palladium cores and highly porous silica hollow shells, were synthesized by direct silica coating and partial etching of the silica layers. High temperature treatment removed all surfactants around the catalyst surface and generated large pores on the silica shells. The resulting Pd@pSiO2 yolk–shell catalysts exhibited extremely high initial turnover frequency of 78000 h–1, as well as excellent reusability of more than 10 times in a standard Suzuki coupling reaction. The catalysts also catalyzed Suzuki reactions with various substrates including bromo- and chlorobenzene very well.
The unique cage complexes [[(Me(4)en)Pd](3)(L)(2)](X)(6) (L = 1,3,5-tris(isonicotinoyloxyethyl)cyanurate; X(-) = BF(4)(-), ClO(4)(-)) were constructed. A single water molecule in a skeletal cage was reversibly associated and dissociated via a combination of the adequate space, polar environment, and conformational flexibility of the cage. In Suzuki-Miyaura C-C cross-coupling reactions, the cage complex showed significant catalytic activity along with the effects of the isolated single water molecule.
We have synthesized Pt@silica/nickel phyllosilicate and Pt@silica yolk-shell nanostructures from NiPt@silica core-shell particles by simple chemical treatments. Silica coating of the NiPt alloy nanoparticles via the microemulsion method yielded spherical NiPt@silica core-shell nanoparticles with an average core diameter of 6.5 nm. Under a reflux condition in water, the core-shell structure transformed into Pt@silica yolk-shell nanoparticles with branched nickel phyllosilicate, which exhibited high surface area and large pore volume. The addition of hydrochloric acid selectively etched the nickel component from the NiPt cores and yielded Pt@silica yolk-shell nanoparticles with single-crystalline platinum cores. The average diameter of the metal cores was reduced to 4.5 nm. In both cases, the nickel components behaved as sacrificial spacers and successfully formed a vacancy between the metal cores and the silica hollow shells.
New functionalized CuO hollow nanospheres on acetylene black (CuO/AB) and on charcoal (CuO/C) have been found to be effective catalysts for C-S bond formation under microwave irradiation. CuO catalysts showed high catalytic activity with a wide variety of substituents which include electron-rich and electron-poor aryl iodides with thiophenols by the addition of two equivalents of K2CO3 as base in the absence of ligands.
Pd/SiO 2 nanobeads containing tiny Pd clusters with a diameter of about 2 nm were prepared via a sol-gel process for SiO 2 by using a water-in-oil microemulsion with Pd complexes and subsequent hydrogen reduction by heat treatment. The Pd/SiO 2 nanostructures were employed in Suzuki coupling reactions with various substrates, and they served as good catalysts in these reactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.