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Un enlace débil y corto metal-metal en un complejo de amidinato de cromo (II)
Azwana R Sadique1, Mary Jane Heeg, Charles H Winter
1Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Journal of the American Chemical Society
|June 26, 2003
Resumen
Se sintetizaron y caracterizaron nuevos complejos de amidinato de cromo. Un complejo, [Cr(tBuNC(CH3)NEt) ]2, forma un dímero con un enlace débil cromo-cromo que se disocia en la solución.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Coordinación Química de la Coordinación
- Síntesis Inorgánica y Síntesis Inorgánica.
Sus antecedentes:
- La química del cromo, particularmente con los ligandos amidinados, es un área de investigación en curso.
- Comprender la unión metal-metal y los efectos de ligando es crucial para el desarrollo de nuevos materiales y catalizadores.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos complejos de amidinato de cromo.
- Investigar las propiedades estructurales, electrónicas y de unión de estos nuevos compuestos.
- Para explorar el comportamiento de la solución y la estabilidad de los complejos diméricos de cromo.
Principales métodos:
- Síntesis de cloruro de cromo (II) con varios reactivos de amidinato de litio.
- Cristalización y difracción de rayos X para la determinación estructural en estado sólido.
- Mediciones de susceptibilidad magnética y espectroscopia de RMN (CP/MAS 13C, 1H) para el análisis electrónico y estructural.
- Peso molecular de la solución y mediciones del momento magnético para evaluar el comportamiento de la solución.
Principales resultados:
- Se sintetizaron con éxito tres nuevos complejos de amidinato de cromo: Cr[tBuNC(CH3) NtBu]2, Cr[iPrNC(CH3) NiPr]2, y [Cr(tBuNC(CH3) NEt) 2) 2.
- Se observaron estructuras monoméricas con geometrías planas tetraédricas y cuadradas para los dos primeros complejos.
- El tercer complejo, [Cr(tBuNC(CH3)NEt) ]2, forma un dímero con un enlace cromo-cromo corto (1.9601(12) Å) y es diamagnético en estado sólido.
- Este dímero se disocia en monómeros paramagnéticos en solución, lo que indica un enlace débil cromo-cromo.
Conclusiones:
- Los complejos de amidinato de cromo sintetizados exhiben diversos motivos estructurales en estado sólido.
- El complejo dimérico [Cr(tBuNC(CH3)NEt)2]2 posee un débil enlace Cr-Cr, disuadiéndose fácilmente en solución.
- Las energías de solvación y las fuerzas de enlace metal-nitrógeno juegan un papel importante en la estabilidad de la forma dimérica.
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