Tendencias sistemáticas en las propiedades electroquímicas de los complejos de hidruro de metales de transición
Benjamin E Rennie1, Renée G Eleftheriades1, Robert H Morris1
1Department of Chemistry, University of Toronto, 80 Saint George St., Toronto, Ontario M5S3H6, Canada.
Journal of the American Chemical Society
|September 17, 2020
Resumen
Este estudio introduce un nuevo método para estimar la acidez de los complejos de hidruro de metales de transición paramagnéticos. Este trabajo proporciona información sobre el diseño del catalizador al predecir la estabilidad del hidruro y la reversibilidad de la oxidación.
Área de la Ciencia:
- Química de coordinación
- Química organometálica
- Catálisis
Sus antecedentes:
- La termodinámica de los hidruros de metales de transición paramagnéticos es crucial para el diseño de electrocatalizadores y catalizadores organometálicos.
- Los métodos existentes para determinar la termodinámica compleja de hidrógenos son limitados, especialmente para los metales 3D abundantes.
Objetivo del estudio:
- Estimar el pKa de los hidritos paramagnéticos en el acetonitrilo (MeCN) por primera vez utilizando la ecuación de la constante de acidez del ligando (LAC).
- Para revelar tendencias sistemáticas en las parejas redox y estimar las energías libres de disociación de enlaces (BDFE ((MH)) para hidritos no oxidados.
- Predecir el potencial electroquímico de oxidación del hidruro y evaluar su reversibilidad.
Principales métodos:
- Desarrolló y aplicó la ecuación de la constante de acidez del ligando (LAC) para estimar los valores de pKa para más de 200 complejos de hidruro.
- Utilizó un ciclo termoquímico con potenciales electroquímicos de la literatura para analizar las tendencias redox.
- Se utilizaron cálculos de la teoría funcional de la densidad (DFT) para validar los valores de pKa estimados para los hidritos seleccionados.
Principales resultados:
- Se ha estimado con éxito la pKa ((LAC-MeCN) para más de 200 complejos de hidruro paramagnético.
- Se han revelado tendencias sistemáticas en los pares redox M{\displaystyle M} , M{\displaystyle M} , V{\displaystyle V} , Mn{\displaystyle Mn} , II{\displaystyle I} , Re{\displaystyle Re} , VI{\displaystyle V} , Re{\displaystyle Re} , IV{\displaystyle III} , M{\displaystyle M} y M{\displaystyle II} .
- Se han establecido correlaciones entre los valores de pKa y la reversibilidad de la oxidación del hidruro, con pKa < 0 indicando oxidación irreversible y pKa > 0 indicando oxidación reversible.
Conclusiones:
- La ecuación de LAC proporciona un método fiable para estimar la termodinámica de los hidruros de metales de transición paramagnéticos.
- Los valores estimados de pKa y BDFE ((MH) son valiosos para predecir el rendimiento y la estabilidad del catalizador.
- Comprender la relación entre el pKa y el comportamiento redox es clave para diseñar electrocatalizadores eficientes y catalizadores organometálicos.
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