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Complejos de cobalto-dinitrógeno con enlaces N-N debilitados.
Keying Ding1, Aaron W Pierpont, William W Brennessel
1Department of Chemistry, University of Rochester, Rochester, New York 14267, USA.
Journal of the American Chemical Society
|June 23, 2009
Resumen
Los complejos de cobalto pueden debilitar el enlace nitrógeno-nitrógeno, especialmente en estados de baja coordinación. Este efecto pi-backbonding es clave para la investigación de la fijación del nitrógeno.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- Química organometálica Química orgánica de los metales.
- Fijación de nitrógeno.
Sus antecedentes:
- Los complejos de cobalto-nitrógeno (N2) reportados exhiben un debilitamiento limitado de los enlaces N-N.
- Lograr un debilitamiento significativo de los enlaces N-N es crucial para la investigación de la fijación del nitrógeno.
Objetivo del estudio:
- Para sintetizar nuevos complejos cobalto-nitrógeno utilizando ligandos dicetiminados.
- Para investigar el efecto del bajo número de coordinación en el debilitamiento de los enlaces N-N en complejos de cobalto.
- Para comparar la capacidad de debilitamiento del enlace N-N del cobalto con el hierro.
Principales métodos:
- Síntesis de nuevos complejos cobalto-nitrógeno con geometrías de tres coordenadas forzadas utilizando ligandos diketiminados.
- Análisis espectroscópico y estructural de los complejos sintetizados.
- Estudios computacionales para comprender las interacciones y enlaces electrónicos.
Principales resultados:
- Se sintetizaron varios nuevos complejos de cobalto-nitrógeno de tres coordenadas (CoNNCo).
- Los complejos de cobalto formalmente no equivalentes mostraron menos debilitamiento de los enlaces N-N en comparación con el hierro.
- Los complejos de cobalto formalmente zerovalentes exhibieron un debilitamiento de los enlaces N-N comparable al del hierro.
- Se identificó la retroconexión pi de cobalto a N2 como el mecanismo para el debilitamiento de los enlaces N-N.
- Se encontró que los cationes de potasio mejoran la donación de densidad de electrones en N2.
Conclusiones:
- El bajo número de coordinación, específicamente la geometría trigonal-planar, es suficiente para inducir el debilitamiento del enlace N-N incluso en el cobalto electronegativo.
- El cobalto puede debilitar efectivamente el enlace N-N en condiciones específicas de baja coordinación, relevantes para la fijación del nitrógeno.
- Las propiedades electrónicas del centro metálico y los cationes auxiliares influyen significativamente en la activación del enlace N-N.
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