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El reordenamiento de normal a anormal y la activación del NHC en los complejos de hierro de tres coordenadas (II)
Benjamin M Day1, Thomas Pugh, Daniël Hendriks
1School of Chemistry, The University of Manchester , Manchester, M13 9PL, U.K.
Journal of the American Chemical Society
|August 28, 2013
Resumen
El calentamiento de complejos de carbenos heterocíclicos (NHC) normales de hierro-N produce estructuras anormales raras de hierro-aNHC. Un complejo sustituido por tert-butilo sufre descomposición térmica a través de las vías de activación C-H y C-N.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Coordinación Química de la Coordinación
- La catálisis de la catálisis.
Sus antecedentes:
- Los carbenos N-heterocíclicos (NHC, por sus siglas en inglés) son ligandos versátiles en la química organometálica.
- Los complejos de hierro con ligandos NHC son de interés debido a la abundancia de hierro y baja toxicidad.
- La distinción entre los modos de coordinación NHC "normales" y "anormales" es crucial para comprender la reactividad.
Objetivo del estudio:
- Para investigar el reordenamiento térmico de un complejo de hierro-NHC normal de tres coordenadas.
- Para sintetizar y caracterizar un raro complejo anormal de hierro-aNHC.
- Explorar la vía de descomposición térmica de un complejo de hierro-NHC sustituido por tert-butilo.
Principales métodos:
- Síntesis y caracterización de complejos de hierro-NHC.
- Tratamiento térmico (calentamiento) de complejos.
- Análisis espectroscópico (por ejemplo, RMN) y cristalografía de rayos X para determinar estructuras.
Principales resultados:
- El complejo normal de hierro-NHC [IPrFeN′′2] se reorganiza a su análogo anormal [aIPrFeN′′2] al calentarse.
- Esta reorganización proporciona un raro ejemplo de un complejo anormal de hierro-aNHC de tres coordenadas.
- El complejo sustituido por tert-butilo [(I(t) Bu) Fe((N′′) 2) se descompone térmicamente para formar un complejo bis (((imidazol) [((t) BuIm) 2Fe(N′′) 2).
- Se propone un mecanismo que involucra la activación consecutiva de enlaces C-H y C-N para la descomposición.
Conclusiones:
- Las condiciones térmicas pueden inducir la reorganización de los ligandos NHC normales a los ligandos NHC anormales en los complejos de hierro.
- Los complejos anormales de hierro-aNHC, en particular los de tres coordenadas, son accesibles.
- La descomposición térmica de ciertos complejos de hierro-NHC puede proceder a través de nuevas vías de activación de C-H y C-N, lo que lleva a productos inesperados.
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