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Conocimientos sobre la unión de aminas a los complejos de adición oxidativa de biarilfosfina y paladio y la

Timothy E Barder¹, Stephen L Buchwald

¹Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. tbarder@mit.edu

Journal of the American Chemical Society

|September 14, 2007

Resumen

Los voluminosos ligandos de biarilfosfina en los complejos de paladio complican la unión de aminas, afectando las vías de aminación catalítica. Nuevos conocimientos mecanicistas revelan un proceso más intrincado de lo que se entendía anteriormente para estas reacciones.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis de la catálisis.
Síntesis orgánica La síntesis orgánica.

Sus antecedentes:

Las reacciones de aminación catalizadas por el paladio son cruciales en la síntesis orgánica.
Los ligandos voluminosos de biarilfosfina (por ejemplo, SPhos, XPhos) son ampliamente utilizados para mejorar la actividad y la estabilidad del catalizador.
Comprender los efectos de los ligandos en los mecanismos de reacción es clave para optimizar los procesos catalíticos.

Objetivo del estudio:

Para investigar la unión de aminas a complejos de adición oxidativa monoligada de paladio con grandes ligandos de biarilfosfina.
Determinar los parámetros termodinámicos y cinéticos que rigen la eliminación reductiva de estos complejos.
Proponer un mecanismo refinado para las reacciones de aminación catalizadas por el paladio que involucran ligandos voluminosos de biarilfosfina.

Principales métodos:

Síntesis y caracterización de complejos de adición oxidativa monoligados L1Pd(Ar)Cl, donde L = SPhos o XPhos.
Estudio de la unión de aminas a estos complejos de paladio.
Análisis termodinámico y cinético de la eliminación reductora de complejos L1Pd ((amido) Ph.

Principales resultados:

La unión de aminas a los complejos de paladio con las voluminosas fosfinas de biarilo (SPhos, XPhos) es más compleja que con los ligandos más pequeños.
Los complejos intermedios Pd(II) con estos ligandos voluminosos no favorecen la unión de aminas en conformaciones favorables.
Se obtuvieron datos termodinámicos y cinéticos para la eliminación reductora para varios complejos de amido.

Conclusiones:

La unión de aminas a los complejos de paladio con los voluminosos ligandos de biarilfosfina está estéricamente obstaculizada.
Se propone un mecanismo más intrincado para las reacciones de aminación catalizadas por el paladio, que se desvía de modelos más simples.
Estos hallazgos proporcionan una visión más profunda de los efectos de los ligandos en la catálisis del paladio.

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