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Ajuste catalítico de un ligando de fosfinoetano para una mayor activación de C-H
Thomas R Cundari1, J Oscar C Jimenez-Halla, Glenn R Morello
1Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, P.O. Box 305070, Denton, Texas 76203-5070, USA. tomc@unt.edu
Journal of the American Chemical Society
|September 6, 2008
Resumen
Este estudio encontró que los complejos de níquel-nitreno con ligandos de fosfina fluorada, como el dfmpe, mejoran significativamente la aminación catalítica de los enlaces C-H al estabilizar la formación de metal-amina. Esto supera las limitaciones de los ligandos dtbpe anteriores.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis de la catálisis.
- Química computacional es la química computacional.
Sus antecedentes:
- La aminación catalítica de los enlaces C-H es crucial para la síntesis de compuestos que contienen nitrógeno.
- Los catalizadores anteriores basados en níquel que utilizaban ligandos de bis ((di-tert-butylphosphino) etano (dtbpe) mostraron limitaciones termodinámicas en la formación de aminas.
- La alta endotermia del rebote radical en los sistemas dtbpeligados obstaculizaba los ciclos catalíticos eficientes.
Objetivo del estudio:
- Investigar nuevos diseños de ligandos para complejos de níquel-nitreno para mejorar la aminación catalítica C-H.
- Para evaluar computacionalmente la viabilidad termodinámica y cinética del uso de ligandos de bis (di) (trifluorometil) fosfino) etano (dfmpe).
- Identificar candidatos prometedores para el precatalizador para una eficiente aminación C-H.
Principales métodos:
- Los cálculos de la Teoría Funcional de Densidad (DFT) se emplearon para modelar las vías de reacción.
- Se calcularon los parámetros termodinámicos (cambios de entalpía) para la abstracción del átomo de hidrógeno y el rebote radical.
- Se analizaron las barreras cinéticas para los pasos clave, incluida la regeneración del ciclo catalítico.
Principales resultados:
- La sustitución de dtbpe por ligandos de dfmpe mejoró dramáticamente el paso de rebote radical, cambiándolo de altamente endotérmico a exotérmico (ΔH = -7.8 kcal/mol).
- El ligando de dfmpe fluorado mejora la fuerza del enlace metal-amina, facilitando la formación de productos.
- Los cálculos indicaron que los complejos de níquel-nitreno con dfmpe son prometedores para la aminación catalítica C-H, con una barrera HAA calculada de 21,3 kcal/mol.
Conclusiones:
- Los complejos de níquel-nitreno apoyados por ligandos de fosfina fluorada, específicamente dfmpe, son muy prometedores para la aminación catalítica C-H.
- La estabilidad mejorada del intermediario metal-amina debido a la ligadura de dfmpe supera los obstáculos termodinámicos anteriores.
- Este trabajo proporciona una base computacional para el diseño de catalizadores de próxima generación para una eficiente funcionalización C-H.
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