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Entrega y eliminación de protones en [Ni(P(R) 2N(R') 2) 2) 2) 2+ catalizadores de producción y oxidación de hidrógeno
Molly O'Hagan1, Ming-Hsun Ho, Jenny Y Yang
1Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, Washington 99352, USA.
Journal of the American Chemical Society
|October 18, 2012
Resumen
El posicionamiento de protones es clave para los catalizadores de hidrógeno basados en níquel. La forma más activa requiere una colocación específica de protones, y la transferencia ineficiente de protones puede limitar la velocidad catalítica en la producción de hidrógeno y las reacciones de oxidación.
Área de la Ciencia:
- La electroquímica es electroquímica.
- La catálisis de la catálisis.
- Química organometálica Química orgánica de los metales.
Sus antecedentes:
- Los complejos de níquel con ligandos de 1,5-diaza-3,7-difosfaciclooctano se investigan para la oxidación y producción de hidrógeno electrocatalítico.
- Las dinámicas de transferencia de protones son cruciales para la eficiencia de estos catalizadores basados en níquel.
Objetivo del estudio:
- Para aclarar el papel de la entrega y eliminación de protones en los ciclos electrocatalíticos de los complejos [Ni(P(R) ((2) N(R') ((2)) ((2))) ((2+).
- Comprender la isomerización de las especies de níquel protonado y su impacto en la actividad catalítica.
Principales métodos:
- Se llevaron a cabo estudios experimentales y teóricos sobre las reacciones de intercambio de protones intermoleculares.
- El análisis se centró en la isomerización de tres isómeros protonados: endo/endo, endo/exo y exo/exo.
Principales resultados:
- El isómero endo/endo es el más catalíticamente productivo debido a la proximidad óptima del protón al centro del níquel.
- Las tasas de isomerización están limitadas por la entrega de protones al complejo o su eliminación del mismo.
- El obstáculo estérico favorece la exoprotonación cinéticamente favorable, lo que lleva a vías menos productivas.
Conclusiones:
- La entrega y eliminación precisas de protones son fundamentales para una electroquímica eficiente de hidrógeno catalizado por níquel.
- Los factores estéricos que influyen en los sitios de protonación afectan significativamente las tasas de rotación catalítica.
- Las ideas mecánicas proporcionan orientación para el diseño de mejoras en la producción de hidrógeno y catalizadores de oxidación.
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