Size-Selective Hydrogenation of Olefins by Dendrimer-Encapsulated Palladium Nanoparticles

摘要: Nearly monodisperse (1.7 ± 0.2 nm) palladium nanoparticles were prepared within the interiors of three different generations hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimers. These dendrimer-encapsulated catalysts (DECs) used to hydrogenate allyl alcohol and four α-substituted derivatives in a 4:1 methanol/water mixture. The results indicate that steric crowding on dendrimer periphery, which increases with generation, can act as an adjustable-mesh nanofilter. That is, by controlling packing density it is possible control access substrates encapsulated catalytic nanoparticle. In general, higher-generation DECs or larger resulted lower turnover frequencies (although some interesting exceptions noted). Although main products olefin hydrogenation reactions corresponding alkanes, ketones also obtained when monosubstituted α-olefins substrates. NMR spectroscopy was measure t...