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Aniones de radicales mononucleares estables de los elementos más pesados del grupo 13: [(tBu2MeSi) 3E.-].
Masaaki Nakamoto1, Tomoki Yamasaki, Akira Sekiguchi
1Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Journal of the American Chemical Society
|May 12, 2005
Resumen
Los investigadores sintetizaron los primeros aniones de radicales mononucleares aislables de los elementos más pesados del grupo 13, el aluminio y el galio. Estos cristales estables de color rojo profundo exhiben geometrías casi planas alrededor de sus centros radicales.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Grupo Principal Química.
- Química Radical La Química Radical es una ciencia
Sus antecedentes:
- Los elementos del grupo 13 suelen exhibir estados de oxidación +3.
- Los aniones radicales mononucleares de los elementos más pesados del grupo 13 están en gran parte inexplorados.
- Los ligandos estéricamente exigentes son cruciales para estabilizar las especies reactivas.
Objetivo del estudio:
- Para sintetizar y caracterizar los primeros aniones radicales mononucleares aislables de aluminio y galio.
- Investigar las propiedades estructurales y electrónicas de estas nuevas especies.
- Para explorar el impacto de los sustitutos sililo voluminosos en la estabilidad de los aniones radicales del grupo 13.
Principales métodos:
- Reducción de un electrón de tris ((di-tert-butylmethylsilyl) aluminio y -gallio utilizando metales alcalinos (Li, Na, K).
- Aislamiento y cristalización de las sales de potasio de los aniones radicales.
- Cristalografía de rayos X para la determinación de la estructura molecular.
- Espectroscopia de resonancia paramagnética de electrones (EPR) para la caracterización electrónica.
Principales resultados:
- Formación y aislamiento de cristales de color rojo intenso, sensibles al aire y a la humedad, de [tBu2MeSi) 3Al*-] (3) y [tBu2MeSi) 3Ga]*- (4) como sales de potasio.
- La cristalografía de rayos X reveló geometrías casi planas alrededor de los centros radicales de Al y Ga.
- Los espectros de EPR mostraron señales características con valores g específicos y constantes de acoplamiento hiperfino para Al-27 y Ga-69/71, consistentes con estructuras planas.
Conclusiones:
- La síntesis y aislamiento exitosos de estos aniones radicales representan un avance significativo en la química de los elementos más pesados del grupo 13.
- Los voluminosos ligandos di-tert-butylmethylsilyl estabilizan efectivamente estos aniones radicales mononucleares sin precedentes.
- La geometría plana en el centro radical es confirmada por datos estructurales y espectroscópicos.
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