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Journal of the Chilean Chemical Society

versão On-line ISSN 0717-9707

Resumo

MELLA, CLAUDIO et al. CHIRAL Rh/SiO2 CATALYSTS FOR ENANTIOSELECTIVE HYDROGENATION REACTIONS: THE ROLE OF (S,S)-DIPAMP AS CHIRAL MODIFIER AND STABILIZER ON METALLIC NANOPARTICLES SYNTHESIS. J. Chil. Chem. Soc. [online]. 2013, vol.58, n.4, pp.2125-2130. ISSN 0717-9707.  http://dx.doi.org/10.4067/S0717-97072013000400050.

Rhodium nanoparticles were successfully stabilized by the (S,S)-1,2-ethanediylbis[(2-ethoxyphenyl)phenylphosphine] ((S,S)-DIPAMP) deposited on SiO2 prepared by a facile reduction and impregnation method. The chiral catalysts obtained were efficient for the enantioselective hydrogenation reactions of prochiral compounds. The catalysts synthesized from [Rh(µ-OMe)(COD)]2 in the presence of different amounts of a ligand used as chiral stabilizer, showed good metal dispersion. As shown by TEM, the metal particle size ranged between 1 and 2 nm using stabilizer and 9.1 nm was achieved without chiral ligand. Other techniques were used to characterize the chiral catalysts such as X-ray diffraction (XRD), electron diffraction, thermogravimetric analysis (TGA) and N2 adsorption-desorption isotherms. (S,S)-DIPAMP was used as the stabilizer of metal particles to prevent growing and agglomeration, and it also acts as chiral modifier inducing enantioselectivity in the asymmetric hydrogenation of 3,4-hexanodione (HD), ethyl pyruvate (EP), ketopantolactone (KP), and acetophenone (AP). Under specific conditions such as 25 °C, 40 bar of H2 and substrate/Rh=100, 1%Rh-(S,S)-DIPAMP/SiO2 chiral catalysts showed excellent catalytic performance with conversion and enantiomeric excess (ee) levels up to 99% and 54% respectively.

Palavras-chave : (S,S)-DIPAMP; stabilized nanoparticles; enantioselective hydrogenation; rhodium; chiral ligand.

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