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Efectos d-orbitales en la no rigidez estereoquímica: Dinámica intramolecular retorcida Ti (IV)
Anna V Davis1, Timothy K Firman, Benjamin P Hay
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|July 20, 2006
Resumen
Los complejos de titanio (IV) tris-catecolatos racemizan más rápido que sus análogos de galio (III) y germanio (IV) debido a su participación en la órbita d. Los cálculos de RMN y DFT a temperatura variable revelan distintas vías de isomerización y barreras cinéticas.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química organometálica Química orgánica de los metales.
- Espectroscopia de RMN y RMN.
Sus antecedentes:
- Los complejos tris-catecolatos son importantes en la química de la coordinación.
- Comprender la dinámica de isomerización es crucial para predecir el comportamiento complejo.
- Estudios anteriores han investigado complejos similares con diferentes iones metálicos.
Objetivo del estudio:
- Para investigar la dinámica de isomerización de los complejos de titanio (IV) tris-catecolatos.
- Para comparar las tasas de racemización de los complejos Ti(IV) con sus análogos Ga(III) y Ge(IV).
- Para dilucidar los mecanismos de isomerización en estos complejos.
Principales métodos:
- Espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable. espectroscopia de resonancia magnética nuclear (RMN) de temperatura variable.
- Análisis de la forma de la línea de 1H espectros de RMN.
- Cálculos de la Teoría Funcional de la Densidad (DFT).
Principales resultados:
- Los complejos de titanio (IV) tris-catecolatos exhiben una racemicidad intramolecular fácil.
- La tasa de racemización de Ti (IV) es más rápida que la de los análogos Ga (III) y Ge (IV).
- Se observaron dos procesos de isomerización distintos para K2[Ti4(3)]2-, atribuidos al giro de Bailar y a los mecanismos de Rây-Dutt.
- Los cálculos de DFT predijeron con precisión las barreras cinéticas relativas y las estructuras de estado fundamental.
Conclusiones:
- La mayor labilidad cinética de los complejos Ti(IV) se atribuye a la participación de los orbitales d en la unión de ligandos.
- El estudio proporciona información sobre las relaciones estructura-actividad de los complejos tris-catecolatos.
- Los hallazgos contribuyen a la comprensión de los mecanismos de isomerización en los compuestos de coordinación.
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