Abstract
Chiral rhodium hybrid nanocatalysts have been prepared by covalent anchorage of pyrrolidine-based diphosphine ligands onto functionalized CNTs. This work constitutes the first attempt at covalent anchoring of homogeneous chiral catalysts on CNTs. The catalysts, prepared with two different chiral phosphines, were characterized by ICP, XPS, N2 adsorption and TEM, and have been tested in the asymmetric hydrogenation of two different substrates: methyl 2-acetamidoacrylate and α-acetamidocinnamic acid. The hybrid nanocatalysts have shown to be active and enantioselective in the hydrogenation of α-acetamidocinnamic acid. A good recyclability of the catalysts with low leaching and without loss of activity and enantioselectivity was observed.
Highlights
Carbon materials have proved to be suitable supports for heterogeneous catalysis, due to their high versatility in terms of textural/surface properties as well as morphology, together with chemical inertness under many conditions, thermal stability and mechanical resistance.[1,2] In particular, nanostructured carbon materials are preferred because of a potential confinement effect.[3,4] Among them, carbon nanotubes (CNTs) showed interesting structures and properties, leading to promising applications as catalyst supports.[5,6] They are usually preferred to other classical carbon materials, like activated carbon, because they are mesoporous
Synthesis of chiral Rh-complexes supported on CNTs
In order to perform the coupling reaction under mild conditions, because of the sensitivity of diphosphine compounds, we have chosen the procedure reported by Nazih et al.,[44] which allows the direct conversion of an N-protected amine into an amide species. This procedure involved the synthesis of diphosphine ligands tailored for immobilization
Summary
Chiral rhodium complexes covalently anchored on carbon nanotubes for enantioselective hydrogenation†. Chiral rhodium hybrid nanocatalysts have been prepared by covalent anchorage of pyrrolidine-based diphosphine ligands onto functionalized CNTs. This work constitutes the first attempt at covalent anchoring of homogeneous chiral catalysts on CNTs. The catalysts, prepared with two different chiral phosphines, were characterized by ICP, XPS, N2 adsorption and TEM, and have been tested in the asymmetric hydrogenation of two different substrates: methyl 2-acetamidoacrylate and α-acetamidocinnamic acid. The hybrid nanocatalysts have shown to be active and enantioselective in the hydrogenation of α-acetamidocinnamic acid. A good recyclability of the catalysts with low leaching and without loss of activity and enantioselectivity was observed
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