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Modificación del catalizador in situ en las reacciones radicales de transferencia de átomos con complejos de rutenio

Juneyoung Lee¹, Jessica M Grandner², Keary M Engle¹

¹Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.

Journal of the American Chemical Society

|May 18, 2016

Resumen

Los complejos de rutenio benzilideno se transforman en una nueva especie activa para las reacciones de transferencia de radicales atómicos (ATR). Esta especie de rutenio generada in situ, no el complejo original, cataliza las reacciones ATR como ATRP y ATRA.

Área de la Ciencia:

Química organometálica
Catálisis
Química de los polímeros

Sus antecedentes:

Los complejos de rutenio benzilideno son catalizadores establecidos de la metástasis de las olefinas.
Estos complejos también muestran actividad en las reacciones de transferencia de radicales atómicos (ATR), incluida la adición de radicales de transferencia atómica (ATRA) y la polimerización de radicales de transferencia atómica (ATRP).
El mecanismo catalítico de los complejos de rutenio benzilideno en las reacciones ATR no se comprende bien, a diferencia de su mecanismo de metástasis de olefinas bien estudiado.

Objetivo del estudio:

Investigar el mecanismo por el cual los complejos de rutenio benzilideno catalizan las reacciones ATR.
Identificar las especies catalíticas activas responsables de la reactividad ATR.
Para comparar la actividad ATR de varios complejos de bencilideno de rutenio.

Principales métodos:

Estudios cinéticos con espectroscopia de RMN 1H para controlar el progreso de la reacción y la transformación de las especies.
Análisis de siete complejos diferentes de bencilideno de rutenio.
Estudios mecánicos y computacionales, incluida la espectroscopia de RMN 1H, 13C y 31P y la cristalografía de rayos X.

Principales resultados:

Los complejos de rutenio benzilideno se convierten rápidamente en nuevas especies inactivas de metástasis en condiciones ATRA.
La preactivación de los complejos de rutenio benzilideno aumenta la reactividad cinética en ATRA, incluso a bajas temperaturas.
Solo los complejos que se transforman fácilmente en especies activas de ATRA catalizan efectivamente el ATRP; otros favorecen la polimerización iniciada por redox.
El catalizador activo en las reacciones ATR es una especie de rutenio inactiva de metástasis formada in situ.

Conclusiones:

El catalizador activo para las reacciones ATR catalizadas por rutenio es una especie de rutenio inativa generada in situ.
Esta especie es distinta del complejo de rutenio benzilideno original.
El análisis estructural sugiere que la especie activa puede ser un complejo RuxCly(PCy3) z.

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