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Atrapar un intermediario de hierro no hemo altamente reactivo que oxigena los fuertes enlaces C-H con
Joan Serrano-Plana1, Williamson N Oloo2, Laura Acosta-Rueda3
1Grup de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT), Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona , Campus de Montilivi, Girona E17071, Catalonia, Spain.
Journal of the American Chemical Society
|November 25, 2015
Resumen
Una nueva especie de hierro hidroxila rápidamente los enlaces C-H con alta selectividad. Este compuesto altamente reactivo, una especie de hierro ((V) oxo, ofrece una actividad catalítica sin precedentes para la funcionalización de alcano.
Área de la Ciencia:
- Química inorgánica
- Química organometálica
- Catálisis
Sus antecedentes:
- Las especies de hierro de alta valencia son cruciales en las reacciones de oxidación biológica.
- Los complejos de hierro no hemo sintéticos imitan estas enzimas pero a menudo carecen de reactividad o estabilidad.
- El desarrollo de catalizadores de hierro altamente reactivos y bien caracterizados para la funcionalización del enlace C-H sigue siendo un desafío significativo.
Objetivo del estudio:
- Para sintetizar y caracterizar una nueva especie de hierro mononuclear altamente reactivo.
- Investigar su mecanismo y reactividad en la activación y hidroxilación de enlaces C-H.
- Para atrapar espectroscópicamente y analizar cinéticamente las especies catalíticas activas.
Principales métodos:
- Reacción de un complejo de hierro mononuclear con el exceso de ácido peracético a temperaturas criogénicas.
- Caracterización espectroscópica que incluye la resonancia paramagnética de electrones (EPR).
- Estudios cinéticos para determinar las velocidades y los mecanismos de reacción (transferencia de átomos de hidrógeno).
Principales resultados:
- Generación de una especie de hierro reactiva sin precedentes (2) en equilibrio entre un complejo de hierro (III) peroxo (2a) y un complejo de hierro (V) oxo (2b).
- La especie 2b exhibe tasas excepcionalmente rápidas para la hidroxilación de enlaces C-H de alcanos a través de la transferencia de átomos de hidrógeno, con estereoretención y regioselectividad.
- La especie activa de hierro ((V) oxo fue atrapada espectroscópicamente y su reactividad interrogada cinéticamente, superando a las especies sintéticas de hierro no hemo de alta valencia conocidas.
Conclusiones:
- El estudio presenta la primera especie de hierro sintético no hemo atrapado espectroscópicamente capaz de hidroxilación C-H estereospecífica y selectiva del sitio.
- La especie activa, principalmente un complejo oxo de hierro, demuestra una notable eficiencia catalítica para activar enlaces C-H fuertes.
- Este trabajo proporciona información crucial sobre el mecanismo de la hidroxilación de C-H mediada por hierro no hemo y abre caminos para el diseño de catalizadores de oxidación avanzados.
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