Abstract
Confinement of palladium nanoparticles inside carbon nanoreactors influences the activity, selectivity and stability of catalytic centres in Suzuki–Miyaura cross-coupling reactions.
Highlights
As the con ned reactions are seemingly independent of the properties of the boronic acid, we propose that nanoscale con nement in GNF affects only the oxidative addition step at the nanoreactor step-edge, with the reactivity of the afforded intermediate dependant on the steric congestion at the reaction locus
We found that the aqueous impregnation of a palladium salt in GNF, followed by gas-phase reduction, enabled near selective con nement of palladium nanoparticles within the interior of graphitised nano bres and the resultant catalytic nanoreactor exhibited attractive catalytic properties in the Suzuki–Miyaura crosscoupling reaction
Through systematic comparison of the yields and distributions of products of reactions using a series of substituted aryl iodides and boronic acids, we have demonstrated that the activity and selectivity of the con ned reactions are sensitive to the steric congestion of the aryl iodides, whereas no in uence of con nement was observed for the reaction of bulky boronic acids
Summary
The con nement of chemical reactions inside carbon nanotubes (CNT) is emerging as a highly versatile tool to control the pathways of molecular transformations and is leading to the formation of new molecules and materials inaccessible by other means.[1,2,3,4] the use of molecular species, such as cyclodextrins, calixarenes, cucurbiturils, supramolecular and coordination cages, micelles and bilayer vesicles,[5,6,7,8,9,10] and extended porous solids, including zeolites,[6,11] to hold chemical reactions has been well established over the last three decades, carbon nanotubes and related hollow carbon nanostructures possess superior chemical,[12] thermal[13] and mechanical stability[13,14] and rely solely upon ubiquitous van der Waals3918 | J. The reactions catalysed by the ligand-free catalysts PdNP@GNF-I and -II resulted in high conversion and selectivity for the cross-coupled product 3aa (Table 2, entries 2 and 3, respectively) but do not allow investigation of the effects of nanoscale con nement due to the location of the catalytic centres almost exclusively on the
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