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Desenmascarar el efecto ligando en la hidrogenación catalizada por manganeso: conocimiento mecanicista y aplicación

Yujie Wang¹, Lei Zhu², Zhihui Shao¹

¹Center of Basic Molecular Science (CBMS), Department of Chemistry , Tsinghua University , Beijing 100084 , China.

Journal of the American Chemical Society

|October 22, 2019

Resumen

Los ligandos NNP-pincer mejoran la reactividad de hidrogenación catalizada por manganeso más que los ligandos PNP-pincer debido a las propiedades electrónicas y estéricas. Este efecto de ligando se confirmó en la hidrogenación de los N-heterociclos, demostrando una amplia aplicabilidad en la catálisis del manganeso.

Área de la Ciencia:

Química organometálica
Catálisis
Química sustentable

Sus antecedentes:

Las reacciones de hidrogenación catalizadas por manganeso han ganado una atención significativa desde 2016.
Los ligandos PNP y NNP de tridentato se emplean comúnmente en sistemas catalizados por Mn.
Los catalizadores de pinza de NNP-Mn muestran una mayor reactividad que las contrapartes de PNP-Mn para sustratos desafiantes.

Objetivo del estudio:

Investigar el origen del efecto ligando observado en la hidrogenación catalizada por Mn.
Confirmar la aplicabilidad general de este efecto de ligando en diferentes tipos de sustrato.
Desarrollar nuevas reacciones de hidrogenación catalizadas por Mn para los heterociclos N.

Principales métodos:

Estudios experimentales para evaluar el rendimiento del catalizador.
Investigaciones teóricas (química computacional) para comprender los efectos electrónicos y estéricos.
Evaluación de los catalizadores NNP-Mn y PNP-Mn para la hidrogenación de diversos sustratos, incluidos los heterociclos N.

Principales resultados:

Los ligandos NNP-pincer son más ricos en electrones y menos estéricamente obstaculizados que los ligandos PNP-pincer.
Este perfil electrónico y estérico de los catalizadores NNP-Mn conduce a una mayor reactividad en la hidrogenación.
La primera hidrogenación catalizada por Mn de N-heterociclos se logró utilizando catalizadores NNP-Mn, con un alto rendimiento (hasta el 99%).

Conclusiones:

El efecto ligando, que favorece al NNP sobre los ligandos PNP, es un fenómeno general en la hidrogenación catalizada por Mn.
Los complejos de pinzas NNP-Mn ofrecen una actividad catalítica superior tanto para sustratos carbonílicos como no carbonílicos.
Este trabajo amplía el alcance de la hidrogenación catalizada por Mn, particularmente para los heterociclos N.

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