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Activación y desactivación de un robusto catalizador de hidrogenación de transferencia de Cp * Ir inmovilizado: un
Grant J Sherborne, Michael R Chapman, A John Blacker
1‡School of Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
Journal of the American Chemical Society
|March 14, 2015
Resumen
Este estudio detalla un catalizador de iridio reciclable para la hidrogenación por transferencia. El análisis espectroscópico revela cómo el catalizador se activa y eventualmente se desactiva, ofreciendo información para el diseño del catalizador.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis de la catálisis.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los catalizadores inmovilizados ofrecen ventajas en la separación y el reciclaje.
- Los complejos de iridio son ampliamente utilizados en la catálisis homogénea, particularmente para la hidrogenación por transferencia.
- Comprender las vías de desactivación del catalizador es crucial para mejorar la longevidad del catalizador.
Objetivo del estudio:
- Para investigar los cambios estructurales y electrónicos de un precatalizador [Cp*IrCl2]2 inmovilizado durante la hidrogenación de transferencia.
- Para aclarar el mecanismo de activación y desactivación del catalizador.
- Establecer un vínculo entre las modificaciones estructurales y el rendimiento catalítico.
Principales métodos:
- Espectroscopia de absorción de rayos X (XAS) en el borde Ir L3, el borde Cl K y el borde K K.
- Experimentos XAS in situ para el monitoreo de procesos catalíticos.
- Envenenamiento por mercurio y experimentos de filtración en caliente para evaluar la lixiviación del catalizador.
Principales resultados:
- El precatalizador [Cp*IrCl2]2 inmovilizado demostró una alta robustez y reciclabilidad (hasta 30 veces).
- La evidencia espectroscópica identificó el intercambio de un ligando de cloruro con un alcóxido como el paso de activación.
- La desactivación se atribuyó al intercambio del segundo ligando de cloruro, formando una especie de alcóxido de potasio-iridato.
Conclusiones:
- El precatalizador activo se forma mediante la sustitución de un ligando de cloruro por un alcóxido.
- La desactivación del catalizador se produce mediante la sustitución del segundo ligando de cloruro.
- Estos hallazgos son relevantes para el diseño de catalizadores de iridio homogéneos y heterogéneos robustos y reciclables.
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