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Mecanismo para la activación del oxígeno molecular por cis- y trans- ((piridina) 2Pd ((OAc) H: Pd ((0) frente a la

Jason M Keith¹, William A Goddard

¹Materials Process and Simulation Center, MC (139-74), California Institute of Technology, Pasadena, California 91125, USA.

Journal of the American Chemical Society

|January 13, 2009

Resumen

La mecánica cuántica revela cómo el oxígeno molecular reacciona con los complejos de hidruro de paladio. La vía Pd(0) se prefiere a la inserción directa tanto para los isómeros cis como para los trans, especialmente con asistencia ácida.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Química cuántica es la química cuántica.
Mecanismos de reacción Mecanismos de reacción

Sus antecedentes:

Los complejos paládio-hidruro son cruciales en la catálisis.
Comprender su reacción con el oxígeno molecular es clave para optimizar los procesos catalíticos.
Los estudios anteriores a menudo se centraban en los ligandos bidentados, dejando incompletas las ideas para los sistemas monodentados.

Objetivo del estudio:

Para dilucidar el mecanismo de reacción del oxígeno molecular con los complejos de hidruro de paladio, específicamente (piridina) -Pd (II) -OAc) H.
Para comparar la inserción directa y las vías intermedias Pd(0) para los isómeros cis y trans.
Para investigar el efecto del ácido acético (HOAc) en el mecanismo de reacción.

Principales métodos:

Se emplearon cálculos mecánicos cuánticos.
Se determinaron las superficies de energía potencial y las estructuras de transición.
El estudio examinó tanto la inserción directa de dioxígeno como las vías que involucran un intermediario Pd{0}.

Principales resultados:

La vía Pd(0) es energéticamente favorecida sobre la inserción directa de dioxígeno para los isómeros cis y trans.
La asistencia ácida (HOAc) reduce significativamente la energía de activación para la vía Pd(0) del isómero trans.
Este estudio es el primero en examinar estos mecanismos para isómeros cis/trans con dos ligandos monodentados y la primera instancia de eliminación reductora asistida por ácido de un plano cuadrado Pd-H.

Conclusiones:

La presencia de dos ligandos monodentados altera el mecanismo de reacción en comparación con los sistemas con ligandos bidentados.
La vía Pd(0) es el mecanismo dominante para la reacción del oxígeno molecular con el complejo estudiado de hidruro de paladio.
La isomerización cis/trans es factible, y la catálisis ácida juega un papel importante en facilitar la reacción para el isómero trans.

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