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El metal como fuente de quiralidad en complejos octaédricos con ligandos tetradentados tripodes
María Carmona1, Ricardo Rodríguez1, Vincenzo Passarelli1,2
1Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza , Pedro Cerbuna 12, 50009 Zaragoza, Spain.
Journal of the American Chemical Society
|January 6, 2018
Resumen
Los complejos metálicos quirales con un ligando trípode logran una configuración absoluta controlada. Estos complejos de rodio enantiopuro catalizan selectivamente las reacciones de Diels-Alder con alta selectividad.
Área de la Ciencia:
- Química orgánica de los metales
- Catalización asimétrica
- Química de coordinación
Sus antecedentes:
- El control de la configuración absoluta de los complejos quiral-metálicos es un desafío significativo en la química sintética.
- Los ligandos tetradentados tripodes ofrecen un andamio prometedor para lograr el control estereocímico alrededor de los centros metálicos.
Objetivo del estudio:
- Desarrollar un método para el control eficiente de la configuración absoluta en complejos quiral-metálicos.
- Para sintetizar complejos de rodio enantiopuro utilizando un ligando tetradentado trípodo.
- Investigar la actividad catalítica enantioselectiva de estos complejos en la reacción de Diels-Alder.
Principales métodos:
- Resolución óptica de los complejos racémicos de rodio mediante el uso de (S) -α-fenilglicina.
- Síntesis de complejos de rodio enantiopuro con la fórmula general [Rh(κ4C,N,N',P-L) A(Solv) ]SbF6]n.
- Catalización de la reacción enantioselectiva de Diels-Alder entre la metacroleína y el ciclopentadieno (HCp).
- Caracterización mediante espectroscopia de resonancia magnética nuclear (RMN) y estudios de teoría funcional de la densidad (TFD).
Principales resultados:
- Se logró un control eficiente de la configuración absoluta de los complejos quiral-metálico utilizando el ligando tetradentado trípodo L.
- La resolución óptica produjo complejos de rodio enantiopuro capaces de catalizar la reacción de Diels-Alder.
- Se obtuvieron relaciones enantioméricas de hasta > 99/1 en la reacción de Diels-Alder entre metacroleína y HCp.
- Los estudios de RMN y DFT aclararon las especies activas, el origen de la enantioselectividad y los detalles mecánicos.
Conclusiones:
- El ligando tetradentado tripodal L es eficaz para controlar la configuración absoluta de los complejos quiral-en-metal.
- Los complejos de rodio enantiopuro sintetizados son catalizadores enantioselectivos altamente efectivos para la reacción de Diels-Alder.
- Se obtuvieron conocimientos mecanicistas detallados sobre el proceso catalítico y el origen de la enantioselectividad.
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