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Sc3+ (o HClO4) Activación de un intermediario no hemo FeIII-OOH para la hidroxilación rápida de ciclohexano y benceno
Subhasree Kal1, Apparao Draksharapu1, Lawrence Que1
1Department of Chemistry and Center for Metals in Biocatalysis , University of Minnesota , 207 Pleasant Street SE , Minneapolis , Minnesota 55455 , United States.
Journal of the American Chemical Society
|April 6, 2018
Resumen
Los iones de escandio (Sc3+) activan los catalizadores de hierro para una hidroxilación eficiente del ciclohexano y el benceno utilizando peróxido de hidrógeno. Esta activación facilita la escisión del enlace O-O, generando un potente oxidante de hierro-oxo para reacciones de oxidación rápidas.
Área de la Ciencia:
- Química inorgánica
- Catálisis
- Reacciones de oxidación
Sus antecedentes:
- Los complejos de hierro se investigan como catalizadores para las reacciones de oxidación.
- El peróxido de hidrógeno (H2O2) es un oxidante común en los procesos catalíticos.
- El benceno y la hidroxilación del ciclohexano son transformaciones químicas difíciles.
Objetivo del estudio:
- Investigar la actividad catalítica de [Fe(β-BPMCN) ((CH3CN) 2+ para la oxidación del ciclohexano y la hidroxilación del benceno.
- Explorar el efecto de Sc3+ y HClO4 en el rendimiento catalítico del complejo de hierro.
- Elucidar el mecanismo de activación e identificar los intermediarios reactivos.
Principales métodos:
- Síntesis y caracterización del complejo de hierro [Fe(β-BPMCN) ((CH3CN) 2+].
- Reacciones de oxidación catalítica del ciclohexano y el benceno utilizando H2O2.
- Estudios espectroscópicos para atrapar e identificar los intermediarios de reacción a bajas temperaturas (-40 °C).
- Estudios cinéticos para determinar las velocidades de reacción y las dependencias.
Principales resultados:
- El complejo de hierro por sí solo mostró poca actividad catalítica para la oxidación del ciclohexano y la hidroxilación del benceno.
- La adición de Sc3+ o HClO4 activó dramáticamente el sistema, permitiendo una rápida hidroxilación de ambos sustratos a -40 °C.
- Un intermedio Fe ((III) - ((η1-OOH) metastable fue atrapado a -40 °C.
- La descomposición de este intermedio dependía de la concentración de Sc3+, lo que sugiere su papel en la heterólisis de enlaces O-O.
Conclusiones:
- Sc3+ y HClO4 actúan como activadores, promoviendo la heterólisis del enlace O-O del intermediario hidroperoxoiron.
- Se propone como oxidante activo una especie de Fe ((V) = O altamente electrófila.
- Este estudio revela una nueva vía de activación para los catalizadores de oxidación a base de hierro, que conduce a especies altamente reactivas comparables a los potentes oxidantes conocidos.
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