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Fijación altamente selectiva de nitrógeno catalizado por Fe a la hidrazina habilitada por Sm (II) Reagentes con
Emily A Boyd1, Jonas C Peters1
1Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States.
Journal of the American Chemical Society
|June 28, 2023
Resumen
Los investigadores controlaron la selectividad del producto en las reacciones de reducción de nitrógeno, favoreciendo a la hidrazina (N2H4) sobre el amoníaco (NH3) mediante el uso de un fuerte reductor de samario. Este descubrimiento ofrece nuevos conocimientos sobre la fijación catalítica del nitrógeno.
Área de la Ciencia:
- Catálisis
- Química inorgánica
- La electroquímica
Sus antecedentes:
- El control de la selectividad del producto en las reducciones multiprotónicas y multielectrónicas de moléculas pequeñas es crucial para la catálisis.
- La selectividad de la reacción de reducción de nitrógeno (N2RR) para el amoníaco (NH3) frente a la hidrazina (N2H4) es poco conocida.
- Los catalizadores de hierro generalmente favorecen la producción de NH3 en N2RR.
Objetivo del estudio:
- Investigar las condiciones que invierten la selectividad en N2RR.
- Para favorecer la producción de hidrazina (N2H4) sobre el amoníaco (NH3) utilizando un catalizador de hierro.
- Comprender la base mecanicista para el control de selectividad en N2RR.
Principales métodos:
- Condiciones desarrolladas para invertir la selectividad de un catalizador de hierro (Fe) de tris (phosphino) borano.
- Se utilizó un núcleo SmII- ((2-pirrolidona) fuertemente reductor con un ligando macrocíclico dianiónico hexadentado (Sm-PH) como donante de átomo de hidrógeno.
- Se han empleado estudios mecanicistas, incluida la espectroscopia, para sondear las vías de reacción.
Principales resultados:
- Se ha conseguido una producción exclusiva de N2H4 (>99:1) sustituyendo los reductores moderados y los ácidos fuertes por el sistema Sm-PH.
- Se mantiene una alta actividad y eficiencia del catalizador, con hasta 69 equivalentes de N2H4 por Fe y un rendimiento de N fijo del 67%.
- Se observó un sobrepotencial de 700 mV más bajo para la producción de N2H4 en comparación con las condiciones selectivas de NH3.
Conclusiones:
- N2H4 es el producto cinético bajo las condiciones impulsadas por Sm desarrolladas.
- La selectividad está determinada por las especies de hidrazido de hierro (FeNNH2): la protonación produce NH3, mientras que la reducción de un electrón produce N2H4.
- Es probable que la unión de SmIII al aniónico FeN2 juegue un papel en la eficacia catalítica.
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