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Russell P Hughes¹, Donghui Zhang, Antony J Ward

¹Department of Chemistry, 6128 Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, USA. rph@dartmouth.edu

Journal of the American Chemical Society

|May 13, 2004

Resumen

Este estudio utilizó el Fluor-19 Nuclear Overhauser Effect Spectroscopy (19F[(1H) HOESY) para determinar las conformaciones de solución de complejos de iridio con ligandos fluoroalquilo secundarios. Los hallazgos revelan las conformaciones escalonadas preferidas, correlacionando la solución y las estructuras de estado sólido.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Química del flúor Química del flúor
Química estructural de las estructuras.

Sus antecedentes:

Los complejos de iridio con ligandos fluoroalquilo son importantes en la catálisis y la ciencia de los materiales.
Comprender la conformación en solución de estos complejos es crucial para predecir su reactividad y propiedades.
Los ligandos fluoroalquilo secundarios introducen complejidad conformacional debido a los estereocentros.

Objetivo del estudio:

Para determinar las conformaciones de solución de los ligandos fluoroalquilo secundarios en complejos de iridio.
Investigar la relación entre las conformaciones en estado sólido y en solución.
Para asignar configuraciones relativas de estereocentro en solución utilizando métodos espectroscópicos.

Principales métodos:

Espectroscopia de Resonancia Magnética Nuclear (RMN), específicamente 19F[(1H) ] HOESY (Fluor-19 Heteronuclear Overhauser Effect Spectroscopy).Espectroscopía de efecto de sobrecarga de fluoruro-19 Heteronuclear Espectroscopía de efecto de sobrecarga de fluoruro-19.
Cristalografía de rayos X para la determinación y comparación de la estructura en estado sólido.
Análisis de las preferencias conformacionales basadas en las interacciones estéricas entre ligandos.

Principales resultados:

Los complejos de iridio adoptan una conformación escalonada, con átomos terciarios de flúor orientados hacia regiones estéricamente obstaculizadas.
Las conformaciones observadas en solución generalmente coinciden con las del estado sólido para los complejos con ligandos CF(CF3) 2.
Se observaron dos diastereómeros para el complejo con el ligando CF (((CF3) (((CF2CF3), con distintas configuraciones de estereocentro relativo asignadas a través de 19F[(1H) ] HOESY.

Conclusiones:

19F[(1H) ] HOESY es una técnica eficaz para determinar las conformaciones de las soluciones y la estereoquímica relativa de los complejos de fluoroalquilo iridio.
Los factores estéricos influyen significativamente en las preferencias conformacionales de los ligandos fluoroalquilo alrededor del centro del metal.
El estudio proporciona información sobre la diversidad estereocímica de los compuestos organometálicos que contienen complejos grupos fluoroalquilo.

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