| Autor: |
Senra, JaquelineD., Malta, Luiz FernandoB., da Costa, Marcelo E.H.M., Michel, RicardoC., Aguiar, Lúcia C.S., Simas, Alessandro B.C., Antunes, O.A.C. |
| Zdroj: |
Advanced Synthesis & Catalysis; October 2009, Vol. 351 p2411-2422, 12p |
| Abstrakt: |
A new approach for the preparation of palladium nanoparticles in water from a renewable source, 2hydroxypropylαcyclodextrin αHPCD, which acts both as a reductant and capping agent, is presented. The palladium nanoparticles were characterized by using dynamic light scattering DLS, transmission electron microscopy TEM and Xray photoelectron spectroscopy XPS, which revealed the formation of spherical particles in the size range of 2–7nm. Further analysis by Fouriertransform infrared spectroscopy FTIR and 1HNMR did not show covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that αHPCD is only physically adsorbed on the nanoparticle surface, presumably through hydrophobic interactions which limit the mutual coalescence of nanoclusters. The catalytic activity was tested in Suzuki, Heck and Sonogashira reactions in neat water, providing good yields and selectivities of coupling products under very low Pd loadings 0.5–0.01mol%. Remarkably, the nanocatalyst showed significant stability hence the aqueous phase remained active for four subsequent runs. The combination of a binding site for substrates the HPCD cavity and a reactive centre Pd core provides a potential to explore functional catalysis in aqueous medium. |
| Databáze: |
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