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El estudio mecanicista de la hidroxilación de C-H catalizada por rutenio revela un camino inesperado para la

James B C Mack¹, Katherine L Walker¹, Sophia G Robinson²

¹Department of Chemistry , Stanford University , 337 Campus Drive , Stanford , California 94305 , United States.

Journal of the American Chemical Society

|January 3, 2019

Resumen

Los complejos de rutenio catalizan la hidroxilación C-H, pero el rendimiento varía con los ligandos. La disociación del ligando y la oxidación a N-óxidos reducen significativamente la eficiencia del catalizador y conducen a la desactivación.

Área de la Ciencia:

Química organometálica
Catálisis
Síntesis orgánica

Sus antecedentes:

Los complejos de rutenio con ligandos de 2,2'-bipiridina (bpy) son catalizadores efectivos para la hidroxilación de C-H.
Existen diferencias significativas de rendimiento entre la 4,4'-di-tert-butil-2,2'-bipiridina (dtbpy) y los ligandos bpy no sustituidos.

Objetivo del estudio:

Investigar los orígenes mecanicistas de las disparidades de rendimiento en la hidroxilación C-H catalizada por Ru.
Comprender las vías de descomposición del catalizador e identificar estrategias para mejorar su diseño.

Principales métodos:

Estudios de la relación estructura-actividad de los ligandos.
Análisis electroquímico y cinético.
Espectrometría de masas de infusión de muestras presurizadas de alta resolución (PSI-MS).

Principales resultados:

Se identificaron múltiples oxidantes activos y tres vías distintas de descomposición del catalizador.
La eficiencia del catalizador (número de rotación) se correlaciona inversamente con las tasas de disociación del ligando.
Los ligandos bpy disociados pueden oxidarse a N-óxidos, que actúan como venenos catalizadores, formando complejos inactivos.

Conclusiones:

Los sustituyentes de ligandos influyen críticamente en la estabilidad y la eficiencia del catalizador en la hidroxilación C-H.
El PSI-MS es una herramienta poderosa para elucidar mecanismos catalíticos complejos.
La comprensión de las vías de desactivación permite el desarrollo de catalizadores Ru de alta eficiencia de próxima generación para la hidroxilación de C-H.

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