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Conocimiento termoquímico de la reducción de CO a CH3OH con los complejos [Re(CO) ](+) y [Mn(CO) ](+)

Eric S Wiedner¹, Aaron M Appel

¹Physical Sciences Division, Pacific Northwest National Laboratory , P.O. Box 999, K2-57, Richland, Washington 99352, United States.

Journal of the American Chemical Society

|May 24, 2014

Resumen

Comprender las barreras termodinámicas para la reducción del monóxido de carbono (CO) a metanol (CH3OH) es crucial. El estudio identifica la adición de H2 a [CpRe (((PPh3) (((NO) (((CO))) como el principal impedimento, con potencial de optimización a través de la variación del ligando y el metal.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis por catálisis.
La termodinámica es la termodinámica.

Sus antecedentes:

La reducción del monóxido de carbono (CO) a metanol (CH3OH) es un proceso clave en la síntesis química y la conversión de energía.
Comprender las limitaciones termodinámicas es esencial para diseñar catalizadores eficientes.

Objetivo del estudio:

Para determinar las energías libres asociadas con la reducción de [CpRe(PPh3) ((NO) ((CO))) ((+)) a CpRe ((PPh3) ((NO) ((CH2OH)).
Identificar las barreras termodinámicas primarias que obstaculizan la reducción de CO.
Explorar estrategias para superar estas barreras utilizando complejos organometálicos.

Principales métodos:

Determinación experimental de las energías libres para la transferencia de protones (H+), hidruro (H-) y electrones (e-) utilizando modelos complejos.
Mediciones de calorimetría para determinar la capacidad del donante de hidruro (ΔG°H(-)).
Voltametría cíclica para estimar los potenciales de oxidación y reducción.
Computaciones de la Teoría Funcional de Densidad (DFT) para analizar las variaciones en las barreras termodinámicas.

Principales resultados:

El pKa para [CpRe (((PPh3) (((NO)) ((CHOH)))) fue estimado en 10.6.
Se encontró que la capacidad donante de hidruro (ΔG°H(-)) de CpRe(PPh3) ((NO) ((CH2OH) era de 58,0 kcal mol ((-1).
Se determinó que la energía libre para la adición de H2 (ΔG°H2) a [CpRe(PPh3) ((NO) ((CO))) ((+) es de +15 kcal mol ((-1), identificada como la barrera termodinámica más significativa.
Los cálculos de DFT mostraron que ΔG°H2 puede ser modulado hasta en 11 kcal mol (−1) a través de la modificación de ligando y metal.

Conclusiones:

La adición de H2 al complejo de carbonilo de renio es el principal obstáculo termodinámico para la reducción de CO.
La modificación de los ligandos auxiliares y el centro metálico en complejos relacionados ofrece una ruta viable para bajar esta barrera.
Estos hallazgos proporcionan información crítica para el desarrollo de catalizadores mejorados para la reducción de CO.

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