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"Carbenos iónicos": síntesis, caracterización estructural y reactividad de los complejos de metilideno de metales de

H Martin Dietrich¹, Karl W Törnroos, Reiner Anwander

¹Department of Chemistry, University of Bergen, Allégaten 41, N-5007 Bergen, Norway.

Journal of the American Chemical Society

|July 20, 2006

Resumen

Nuevos grupos organometálicos producen complejos de metilideno sin aluminio. Estos complejos facilitan reacciones tipo Tebbe y muestran reactividad de metales de tierras raras en la polimerización.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Complejos de metales de tierras raras.
Catálisis de polimerización por catálisis de polimerización.

Sus antecedentes:

Se sintetizaron racimos polinucleares que contienen aluminio con la fórmula {Cp*Y[(mu-Me) 2AlMe2](mu-Cl) }2 y {Cp*6La6[(mu-Me) 3AlMe]4(mu3-Cl) 2(mu2-Cl) 6}
Estos grupos presentan ligandos puentes de metilo y cloruro mezclados.

Objetivo del estudio:

Para sintetizar nuevos complejos de metilideno "libres de aluminio".
Investigar la reactividad de estos nuevos complejos en las reacciones de metilenación y polimerización.

Principales métodos:

Tratamiento de los racimos polinucleares de tetrametilaluminato con soluciones de tolueno/THF.
Caracterización de los complejos de metilideno trinuclear resultantes utilizando análisis de estado sólido.
Reacciones con cetonas, aldehídos y gamma-valerolactona para evaluar la reactividad.

Principales resultados:

Se han producido con éxito complejos de metilideno "libres de aluminio" [Cp*3Ln3(mu-Cl) 3(mu3-Cl) ((mu3-CH2) ((THF) 3) (Ln = Y, La).
Los complejos son isostruturales y contienen una unidad CH22- nucleofílica de tipo Schrock estéricamente blindada.
Los complejos de metilideno demostraron una metilenación similar a Tebbe con compuestos de carbonilo y una rápida polimerización de la gamma-valerolactona.

Conclusiones:

Los complejos sintetizados representan una nueva clase de compuestos de metilideno sin aluminio.
La unidad de metilideno nucleófilo es altamente reactiva, lo que permite reacciones eficientes de metilenación.
La polimerización observada de la gamma-valerolactona pone de relieve la reactividad intrínseca de los metales de tierras raras en la catálisis.

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