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Conversión catalítica de nitrógeno en amoníaco mediante complejos de osmio y rutenio

Javier Fajardo¹, Jonas C Peters¹

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

Journal of the American Chemical Society

|October 28, 2017

Resumen

Los complejos de rutenio (Ru) y osmio (Os) ahora catalizan la fijación de nitrógeno (N2RR), convirtiendo el N2 en amoníaco (NH3). El sistema de osmio es el más activo, produciendo más de 120 equivalentes de NH3, con un intermediario hidrazido propuesto.

Área de la Ciencia:

Química organometálica
Catálisis
Fijación de nitrógeno

Sus antecedentes:

Los complejos de rutenio (Ru) y osmio (Os) son cruciales en la química del nitrógeno de los metales de transición.
Sin embargo, no han mediado previamente la fijación catalítica del nitrógeno (conversión de N2 a amoníaco, N2RR).
Los complejos M-NxHy no se han derivado de la protonación de los precursores M-N2.

Objetivo del estudio:

Determinar los factores que influyen en la catálisis N2RR.
Informar sobre los complejos isostruturales de tris (fosfino) sililo Ru y Os para el N2RR.
Para comparar las actividades catalíticas con un complejo isostrutural de hierro (Fe).

Principales métodos:

Síntesis de complejos isostruturales de tris (fosfino) sililo Ru, Os y Fe.
Experimentos catalíticos de N2RR utilizando Cp*2Co como reductor y [H2NPh2][OTf] como fuente de ácido.
Caracterización estructural de los intermedios, incluida la protonación de Os-N2- a una especie de hidrazido Os=NNH2+.
Caracterización de los hidruros de óxido formados durante la catálisis.

Principales resultados:

El sistema Osmium demostró la mayor actividad, liberando más de 120 equivalentes de amoníaco (NH3) por centro Os en un solo lote.
Los complejos isostruturales de Ru y Fe generaron un mínimo de NH3 en condiciones idénticas.
La protonación del complejo Os-N2 produjo una especie hidrazida estructuralmente caracterizada como Os=NNH2+.
Se identificaron los hidratos de óxido inactivo como subproductos catalíticos.

Conclusiones:

Los complejos de tris (fosfino) sililo Ru y Os median el N2RR catalítico, siendo Os el más activo.
La especie Os=NNH2+ hidrazido es un intermediario plausible en el ciclo catalítico.
Este trabajo proporciona información sobre los factores que rigen la catálisis N2RR utilizando complejos Ru y Os.

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