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Síntesis, caracterización estructural y espectroscópica y reactividades de los complejos mononucleares de cobalto
Jaeheung Cho1, Ritimukta Sarangi, Hye Yeon Kang
1Department of Bioinspired Science, Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea.
Journal of the American Chemical Society
|November 11, 2010
Resumen
Este estudio sintetizó y caracterizó los complejos de cobalto (III) -peroxo con ligandos tetraazamacrocíclicos, revelando su unión lateral y su reactividad en las reacciones de oxidación y transferencia de O (II), influenciadas por el tamaño del anillo del macrociclo.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química bioorgánica Química bioorgánica.
- La catálisis es la catálisis.
Sus antecedentes:
- Los aductos de metal-dióxido son intermedios cruciales en la activación del dioxígeno por metalloenzimas y sistemas biomiméticos.
- Comprender la estructura y la reactividad de estos intermedios es clave para desarrollar catalizadores eficientes.
Objetivo del estudio:
- Para sintetizar y caracterizar los complejos mononucleares de cobalto (III) -peroxo con diferentes tamaños de anillo de ligando tetraazamacrocíclico.
- Investigar la reactividad de estos complejos en la oxidación de aldehídos y en las reacciones de transferencia de O2−.
- Para dilucidar la influencia del tamaño del anillo del ligando macrocíclico en la reactividad compleja.
Principales métodos:
- Síntesis de los complejos mononucleares de cobalto (III) -peroxo, (Co) -12-TMC (O) -2)) y (Co) -13-TMC (O) -2) y (Co) -13-TMC (O) -2) y (Co) -13-TMC (O) -2.
- Caracterización mediante técnicas espectroscópicas (por ejemplo, resonancia Raman) y cristalografía de rayos X.
- Evaluación de la reactividad en la oxidación del aldehído y la transferencia de O2 a un complejo de manganeso II.
Principales resultados:
- Se confirmó que el ligando peroxo se une de manera lateral en η(2), con distancias de enlace O-O de ~ 1,439 Å.
- La espectroscopia Raman de resonancia mostró una frecuencia de estiramiento de enlace O-O de 902 cm ((-1).
- La reactividad tanto en la oxidación del aldehído como en la transferencia de O(2) dependía del tamaño del anillo del ligando macrocíclico, con [Co(13-TMC)(O(2))](+) exhibiendo una reactividad más alta que [Co(12-TMC)(O(2))](+).
Conclusiones:
- Los complejos cobalto-peróxido sintetizados sirven como modelos bien definidos para los intermediarios de activación de dioxígeno.
- El tamaño de los anillos de los ligandos macrocíclicos juega un papel importante en la modulación de la reactividad de los complejos cobalto-peróxido en las reacciones de oxidación y transferencia de O2−.
- Estos hallazgos contribuyen a la comprensión de los mecanismos de las metalloenzimas y al diseño de nuevos catalizadores de oxidación.
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