Estudio experimental y teórico sobre catalizadores enantioselectivos heterogéneos: análisis DFT del precursor (-)-MenSnBu3 y del comportamiento del catalizador obtenido en la hidrogenación de acetofenona.

JOSÉ F. RUGGERA; VIRGINIA VETERE; OSMAR A. FERRETTI; MÓNICA L. CASELLA

Gramado, Brasil

Simposio; XX Simposio Iberoamericano de Catálisis; 2006

In the present work it is introduced the theoretical modelling of tri-butyl-menthyltin molecule (MenSnBu3), which is used to obtain Pt-based chiral heterogeneous catalysts employed in acetophenone hydrogenation. The conformational study of the molecule was carried out by means of Molecular Dynamics, Molecular mechanics and the Density Functional Theory (DFT) to perform calculations of the binding energy (BE) of each one of the Sn-C bonds, three with each one of the butyl (Bu) groups and the other one with the menthyl (Men) group. In all the cases it is obtained as a result, that the most stable is the bond between Sn and the C atom corresponding to the menthyl group. According to this, when the reaction of the organotin compound and the supported platinum takes place, some of the butyl groups would be lost before the menthyl group does. These results agree with the experiments of the enantioselective hydrogenation of acetophenone (an enantiomeric excess of 23% is obtained towards (S)-1-phenylethanol), that can only be consequence of the presence of some kind of chiral center in the catalytic phase.