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Estimación de la acidez de los complejos de hidruro y dihidrógeno de metales de transición mediante la adición de las
1Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada.
Journal of the American Chemical Society
|January 14, 2014
Resumen
Una nueva ecuación estima la acidez (pKa) de los complejos de hidruro de metal de transición y dihidrógeno en varios disolventes. Este método ayuda a comprender la acidez de los complejos metálicos naturales e industrialmente relevantes.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química organometálica Química orgánica de los metales.
- Química Física es la química física.
Sus antecedentes:
- Los complejos de hidruro y dihidrógeno de metales de transición son cruciales en la catálisis y en los sistemas biológicos.
- Los valores precisos de pKa son esenciales para comprender su reactividad y estabilidad.
- Los métodos existentes para la determinación de pKa pueden ser complejos y consumir mucho tiempo.
Objetivo del estudio:
- Desarrollar una ecuación predictiva simple y ampliamente aplicable para el pKa de los complejos de hidruro y dihidrógeno de metales de transición.
- Proporcionar una herramienta para estimar los valores de pKa en tetrahidrofurano y otros disolventes.
- Para permitir una rápida evaluación de la acidez de estos complejos en diversas aplicaciones.
Principales métodos:
- Un enfoque cuantitativo de la relación estructura-propiedad (QSPR) utilizando una simple ecuación aditiva: pKa(THF) = AL + Ccharge + Cnd + Cd6.
- Se determinaron las constantes de acidez (AL) para 13 tipos de ligandos comunes y se correlacionaron con los parámetros de ligandos electroquímicos (EL) de Lever para los ligandos neutros.
- Se aplicaron correcciones para la carga compleja (Ccharge), la fila periódica del metal de transición (Cnd) y los iones metálicos octaédricos d(6) (Cd6).
Principales resultados:
- La ecuación estima con precisión más de 170 valores de pKa de la literatura para una amplia gama de complejos de metales de transición (Cr a Ni, Mo, Ru a Pd, W a Pt).
- El método proporciona buenas estimaciones con una desviación estándar de 3 unidades de pKa en un rango de pKa de 0 a 50.
- El enfoque también estima la fuerza de base de la forma compleja desprotonada.
Conclusiones:
- La ecuación desarrollada ofrece un método fácil y confiable para predecir la acidez de los complejos de hidruro y dihidrógeno de metales de transición.
- Esta herramienta predictiva es valiosa para aplicaciones en la comprensión de las hidrogenasas, la catálisis y la investigación de la energía del hidrógeno.
- Se observaron desviaciones para complejos con ligandos quelantes con ángulo de mordedura voluminosos o grandes, lo que sugiere áreas para refinamiento futuro.
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