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Comprender los mecanismos de las reacciones de hidrogenación y deshidrogenación catalizadas por cobalto

Guoqi Zhang¹, Kalyan V Vasudevan, Brian L Scott

¹Chemistry and Materials Physics Applications Divisions, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

Journal of the American Chemical Society

|May 30, 2013

Resumen

Los catalizadores de cobalto con ligandos de pinza muestran actividad en la hidrogenación y deshidrogenación. La cooperación metal-ligando es clave para la hidrogenación de cetonas, pero no para la hidrogenación de olefinas o la deshidrogenación de alcohol.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis de la catálisis.
Coordinación Química de la Coordinación

Sus antecedentes:

Los complejos de cobalto con ligandos de pinza se exploran para aplicaciones catalíticas.
La cooperación metal-ligando es un mecanismo propuesto en la catálisis.

Objetivo del estudio:

Para sintetizar y caracterizar cobalto (II) complejos de alquilo con alifáticos PNP ligandos de pinza.
Investigar la actividad catalítica de estos complejos en las reacciones de hidrogenación y deshidrogenación.
Para aclarar el papel del grupo N-H en la catálisis cooperativa metal-ligando.

Principales métodos:

Síntesis y caracterización de cobalto (II) complejos de alquilo.
Pruebas catalíticas para la hidrogenación de las olefinas y cetonas.
Pruebas catalíticas para la deshidrogenación sin aceptor de alcoholes.
Espectroscopia de RMN para el monitoreo de la reacción.

Principales resultados:

El complejo catiónico de cobalto (II) alquilo (PNHP) (Cy) (Co) (CH2SiMe3) (BAr) (F) es un precatalizador activo para la hidrogenación y deshidrogenación.
Un complejo relacionado que carece del grupo N-H mostró actividad en la hidrogenación de olefinas pero no en la hidrogenación de cetonas.
Se identificó un intermediario de cobalto (III) como un estado de reposo en la deshidrogenación del alcohol.
La cooperación metal-ligando estuvo implicada en la hidrogenación de cetonas pero no en la hidrogenación de olefinas ni en la deshidrogenación de alcohol.

Conclusiones:

El grupo N-H del ligando de la pinza juega un papel crucial en la catálisis cooperativa del ligando metálico, particularmente en la hidrogenación a temperatura ambiente de las cetonas.
Los complejos de pinzas de cobalto son catalizadores versátiles para la hidrogenación y la deshidrogenación, con mecanismos que varían dependiendo de la reacción y la estructura del ligando.

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