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El equilibrio de isomerización entre el cloruro de rutenio cis y el cloruro de trans de los catalizadores de la
Diego Benitez1, William A Goddard
1Materials and Process Simulation Center, Beckman Institute, California Institute of Technology, Pasadena, California 91125, USA.
Journal of the American Chemical Society
|September 1, 2005
Resumen
Este estudio utiliza la mecánica cuántica para investigar la isomerización del catalizador de rutenio en diferentes disolventes. Los resultados muestran que la elección del disolvente puede aislar isómeros específicos del catalizador de la metátesis de la olefina de rutenio.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química computacional es la química computacional.
Sus antecedentes:
- Los catalizadores de la metátesis de las olefinas son cruciales en la síntesis orgánica.
- Comprender la isomerización del catalizador es clave para controlar la reactividad.
- Los catalizadores basados en rutenio son ampliamente utilizados, pero su isomerismo necesita más estudios.
Objetivo del estudio:
- Para investigar la isomerización cis-trans de cloruro de un catalizador de metátesis de olefina de rutenio.
- Para dilucidar el papel del disolvente en la influencia de las proporciones de isómero catalizador y la estabilidad.
- Proporcionar conocimientos teóricos sobre las observaciones experimentales del comportamiento del catalizador.
Principales métodos:
- Utilizó la mecánica cuántica, específicamente la teoría funcional de la densidad B3LYP (DFT).
- Incorporó la aproximación del continuo de Poisson-Boltzmann (PBF) para modelar los efectos del disolvente.
- Calculadas las energías de activación relativas y las energías libres de isomerización.
Principales resultados:
- Las geometrías predichas se alinean con los datos experimentales.
- En cloruro de metileno, se calculó DeltaG = -0.70 kcal/mol y una relación cis:trans de 76:24, que coincide estrechamente con los valores experimentales.
- En el benceno, la proporción cis:trans predicha es de 4:96, consistente con la observación experimental de sólo el isómero trans.
Conclusiones:
- La polaridad del disolvente influye significativamente en el equilibrio de isomerización cis-trans del catalizador de rutenio.
- Las energías de activación relativas calculadas explican las diferencias observadas en las tasas de iniciación del catalizador.
- Se predice que las altas proporciones de isómeros individuales serán aislables mediante una selección juiciosa del disolvente.
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