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Angewandte Chemie International Edition, Volume 52, Issue 5, pages 1481–1485, January 28, 2013.
Dr. Takato Mitsudome, Yusuke Takahashi, Dr. Satoshi Ichikawa, Dr. Tomoo Mizugaki, Prof. Dr. Koichiro Jitsukawa,Prof. Dr. Kiyotomi Kaneda
Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1–3, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan) and
Institute for NanoScience Design Center, Osaka University, Toyonaka, Osaka 560-8531 (Japan) and
Research Center for Solar Energy Chemistry Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka 560-8531 (Japan).
Abstract
Catalysts with a sheltered upbringing: Novel core–shell nanocomposite catalysts consisting of active metal nanoparticles encapsulated by macroligands have been prepared. They have Pd nanoparticles (PdNPs) as an active core and shell ligands having sulfoxide moieties coordinated to the PdNPs. The shell protects the catalyst from coordination by alkenes and allows the lead-free selective semihydrogenation of a wide range of alkynes without any additives (see scheme).
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
Core-shell nanocomposite catalysts for semihydrogenation of alkynes were successfully synthesized by the encapsulation of Pd nanoparticles using a sulfoxide matrix (MPSO) (Pd@MPSO/SiO2). The Pd@MPSO/SiO2 catalysts efficiently promoted the Pb-free selective semihydrogenation of a wide range of alkynes without any additives under mild reaction conditions (1 atm of H2 at 30oC-50oC). The sulfoxide moiety in the shell acted as a ligand for the core-Pd nanoparticles, allowing the semihydrogenation of a wide range of internal and terminal alkynes. For example, (Z)-3-hexen-1-ol (leaf alcohol) and (Z)-methyl jasmonate, which are commercially important products for fragrances, were obtained in 97% and 95% yields, respectively. Moreover, in all cases, the overhydrogenation and isomerization of the products barely occurred and high selectivity for (Z)-alkenes was maintained even after complete consumption of the alkynes. This catalytic performance is quite different from other Pb-free catalyst systems previously reported where the hydrogenation of alkene products occurred after complete consumption of the alkynes. Moreover, the Pd@MPSO/SiO2 catalysts were simply recovered and reusable while maintaining high activity and selectivity.
The developed core-shell nanocomposite catalysts are promising for green semihydrogenation processes due to the following advantages: 1) high catalytic activity and selectivity, 2) wide scope of substrates (applicable to both internal and terminal alkynes), 3) no contamination with metals (no metal leaching), 4) catalyst reusability (high durability) and 5) easy handling (no need for additives and suppression of the overhydrogenation of the products).
