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La no inocencia de haluro y la fotorreducción directa de Ni (II) permiten el acoplamiento de cloruros de arilo en
Cameron H Chrisman1, Max Kudisch1,2, Katherine O Puffer1
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States.
Journal of the American Chemical Society
|May 19, 2023
Resumen
Este estudio revela el papel crucial del enfriamiento oxidativo en las reacciones fotorredóxicas / catalizadas por níquel, demostrando cómo la comprensión de este mecanismo mejora la eficiencia del catalizador para desafiar las reacciones de acoplamiento cruzado.
Área de la Ciencia:
- Fotocatálisis
- Química organometálica
- Mecanismos de reacción
Sus antecedentes:
- La doble catálisis fotoredox/níquel es vital para el acoplamiento cruzado impulsado por la luz.
- Los mecanismos de fotocatalizador (PC) generalmente implican el apagado reductivo o la transferencia de energía.
- Los ciclos de enfriamiento oxidativo son menos conocidos, especialmente con potentes fotocatalizadores reductores.
Objetivo del estudio:
- Investigar las vías mecanicistas de un sistema unificado dual fotorredóxido/Ni catalizado.
- Observar directamente los eventos de apagado oxidativo en estas reacciones.
- Aclarar cómo las ideas mecanicistas pueden mejorar la eficiencia catalítica.
Principales métodos:
- Se utilizó la espectroscopia de absorción transitoria de nanosegundos para observar el apagado oxidativo.
- Se han realizado estudios de especiación para analizar la formación de complejos de níquel.
- Análisis cinético empleado para comprender el papel de los intermediarios.
Principales resultados:
- Se observa directamente el enfriamiento oxidativo de los fotocatalizadores (por ejemplo, Ir ((ppy) 3).
- Identificó que la especiación de níquel y la unión de ligandos afectan las tasas de fotorreducción.
- Se ha demostrado que la persistencia del par de iones Ir (IV) / Ni (I) es clave para la cinética de la reacción.
- Se ha demostrado que los aniones halogenados pueden regenerar el fotocatalizador.
Conclusiones:
- El enfriamiento oxidativo es una vía viable e importante en estos sistemas catalíticos.
- La comprensión mecanicista condujo al descubrimiento de que la adición de cloruro mejora drásticamente las tasas de reacción.
- Los hallazgos permiten un acoplamiento eficiente de cloruros de arilo, ampliando el alcance de la catálisis dual.
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