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Complejos catiónicos de carbenos heterocíclicos de tungsteno-oxo-alquilideno-N: catalizadores de la metátesis de las

Roman Schowner¹, Wolfgang Frey¹, Michael R Buchmeiser¹

¹§Institute of Polymer Chemistry and ‡Institute of Organic Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.

Journal of the American Chemical Society

|May 5, 2015

Resumen

Los investigadores desarrollaron nuevos catalizadores de carbenos heterocíclicos (NHC) de tungsteno-oxo-alquilideno-N para la metátesis de olefinas. Estos catalizadores muestran una alta actividad y estabilidad, lo que permite transformaciones químicas eficientes.

Área de la Ciencia:

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

Sus antecedentes:

Los ligandos del carbeno N-heterocíclico (NHC) son cruciales en la química organometálica moderna.
Los catalizadores a base de tungsteno se exploran para diversas transformaciones, incluida la metátesis de olefinas.
El desarrollo de catalizadores estables y activos es clave para aplicaciones sintéticas eficientes.

Objetivo del estudio:

Informar sobre la síntesis, estructura y actividad de la metátesis de olefinas de nuevos catalizadores neutros y catiónicos de W-oxo-alquilideno-NHC.
Para investigar las vías de activación y la estabilidad de estos complejos de tungsteno.
Para evaluar el rendimiento catalítico en diversas reacciones de metátesis de olefinas.

Principales métodos:

Síntesis de complejos neutros de W-oxo-alquilideno-NHC.
Caracterización estructural que incluye la determinación de la geometría de la esfera del ligando (octaédrica o trigonal bipiramidal).
Activación de complejos neutros utilizando ácidos de Lewis (por ejemplo, AlCl3) o metatesis de sales con sales de plata o sodio para formar especies catiónicas.
Evaluación de la actividad catalítica en las reacciones de metástasis de olefinas.

Principales resultados:

Los catalizadores neutros de W-oxo-alquilideno-NHC fueron sintetizados con altos rendimientos (hasta el 90%).
Los complejos W catiónicos, activos en la metatesis de olefinas, se prepararon a través de reacciones de sustitución, mostrando una mayor estabilidad.
Estos catalizadores catiónicos demostraron una alta actividad, logrando números de facturación de hasta 10.000.
Se observó una catálisis efectiva para alquenos con varios grupos funcionales (nitrilo, secamina, tioéter).

Conclusiones:

Se han desarrollado con éxito los primeros catalizadores neutros y catiónicos de W-oxo-alquilideno-NHC para la metástasis de olefinas.
Se puede acceder a catalizadores estables y altamente activos de tungsteno catiónico a través de estrategias sintéticas específicas.
Estos catalizadores representan un avance significativo en la metátesis de olefinas, ofreciendo un amplio alcance de sustrato y alta eficiencia.

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