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Caracterización de un intermediario FeN-NH2 relevante para la reducción catalítica de N2 a NH3

John S Anderson¹, George E Cutsail², Jonathan Rittle¹

¹Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.

Journal of the American Chemical Society

|May 23, 2015

Resumen

Los complejos de hierro ahora pueden ser protonados, formando una especie de hidrazido doblemente protonado. Este hallazgo proporciona información clave sobre los mecanismos de reducción de nitrógeno mediados por el hierro, lo que hace avanzar la química bioinorgánica.

Área de la Ciencia:

Química Inorgánica La Química Inorgánica es la química inorgánica.
Química bioorgánica Química bioorgánica.
Química organometálica Química orgánica de los metales.

Sus antecedentes:

Los metales de transición como el Mo y el W facilitan la reducción del nitrógeno (N2) a amoníaco (NH3).
La protonación directa de complejos de hierro (Fe) -N2 a intermedios estables ha sido un desafío.
Comprender el papel del hierro en la reducción de N2 es crucial para la síntesis de amoníaco.

Objetivo del estudio:

Para investigar los pasos iniciales de la reducción de nitrógeno mediada por un complejo de hierro.
Para caracterizar el producto de la adición de ácido a un complejo de hierro-nitrógeno.
Para dilucidar el mecanismo de la fijación de N2 catalizada por el hierro.

Principales métodos:

La adición de ácido a baja temperatura a [(TPB) Fe (((N2) ][Na ((12-corona-4) ].
Caracterización espectroscópica: resonancia paramagnética de electrones (EPR), resonancia doble electrón-nuclear (ENDOR), espectroscopia de Mössbauer, estructura fina de absorción de rayos X extendida (EXAFS).
Análisis computacional utilizando la Teoría Funcional de la Densidad (DFT).

Principales resultados:

Se generó una nueva especie de hierro S = 1/2 mediante la adición de ácido.
La especie fue identificada como un complejo de hidrazido doblemente protonado (((2-), [(TPB)FeN-NH2](+), con un enlace triple Fe-N.
Este intermedio proporciona evidencia de una vía distal (tipo Chatt) en la reducción de N2 mediada por el hierro.

Conclusiones:

El estudio caracterizó con éxito un intermediario clave en la reducción de nitrógeno mediada por el hierro.
Los hallazgos apoyan un mecanismo distal para los pasos iniciales de protonación.
Este trabajo avanza en la comprensión de la fijación de nitrógeno por complejos de hierro.

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