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Hydroxypropyl‐α‐Cyclodextrin‐Capped Palladium Nanoparticles: Active Scaffolds for Efficient Carbon‐Carbon Bond Forming Cross‐Couplings in Water
Author(s) -
Senra Jaqueline D.,
Malta Luiz Fernando B.,
da Costa Marcelo E. H. M.,
Michel Ricardo C.,
Aguiar Lúcia C. S.,
Simas Alessandro B. C.,
Antunes O. A. C.
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200900348
Subject(s) - chemistry , palladium , sonogashira coupling , dynamic light scattering , nanoparticle , catalysis , aqueous solution , nanoclusters , x ray photoelectron spectroscopy , fourier transform infrared spectroscopy , adsorption , cyclodextrin , photochemistry , chemical engineering , polymer chemistry , organic chemistry , engineering
A new approach for the preparation of palladium nanoparticles in water from a renewable source, 2‐hydroxypropyl‐α‐cyclodextrin (α‐HPCD), 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 X‐ray photoelectron spectroscopy (XPS), which revealed the formation of spherical particles in the size range of 2–7 nm. Further analysis by Fourier‐transform infrared spectroscopy (FT‐IR) and 1 H NMR did not show covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that α‐HPCD 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 (0.5–0.01 mol%). 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.