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Isómeros de espín y isomerización de ligandos en un complejo de cobalto de tres coordenadas
Malik H Al-Afyouni1, Elizaveta Suturina2,3, Shubhrodeep Pathak2
1Department of Chemistry, University of Rochester , Rochester, New York 14618, United States.
Journal of the American Chemical Society
|August 13, 2015
Resumen
Este estudio revela un complejo de cobalto que cambia rápidamente entre estados de espín y estructuras. Este comportamiento del ligando hemilabil ofrece nuevos conocimientos sobre la catálisis de metales de transición y la dinámica de espín.
Área de la Ciencia:
- Química organometálica
- Catálisis
- Cruce de espín
Sus antecedentes:
- Los ligandos hemilabílicos son cruciales en la catálisis de metales de transición para crear sitios de coordinación accesibles.
- La labilidad del ligando puede influir en las propiedades electrónicas de los centros metálicos, incluidos los estados de espín.
- Comprender los cambios de estado de giro es clave para controlar la actividad catalítica y las vías de reacción.
Objetivo del estudio:
- Investigar un sistema de cobalto exhibiendo hemilabilidad y rápida interconversión de estado de espín.
- Caracterización de un nuevo complejo de cobalto (I) monocarbonilo con un modo inusual de unión de diketiminato.
- Para aclarar el mecanismo y la termodinámica de la interconversión de isómeros de espín.
Principales métodos:
- Síntesis y caracterización del complejo de cobalto ((I) monocarbonilo L ((tBu) Co ((CO).
- Espectroscopia de la solución (NMR, absorción electrónica) para estudiar las poblaciones y la dinámica de los isómeros de espín.
- Modelado computacional (cálculos de puntos de cruce de energía mínima) para determinar las vías de reacción.
Principales resultados:
- El complejo existe como un estado singlet en forma sólida, pero una población significativa de estado triplet en solución.
- La interconversión rápida entre los isómeros de espín singlet y triplet ocurre incluso a bajas temperaturas.
- Un mecanismo único de "deslizamiento" del ligando diquetiminado, en lugar de la disociación, facilita la transición.
Conclusiones:
- El sistema de cobalto explorado demuestra un fácil acceso a múltiples estados de espín.
- La hemilabilidad del ligando y el cambio de estado de espín están intrínsecamente vinculados.
- Este trabajo proporciona un mapa mecanicista y termodinámico detallado de la interconversión de isómeros de espín en complejos hemilabílicos.
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