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The Synthesis of [Sn10(Si(SiMe3)3)4]2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique
Published on: November 28, 2016
Aislamiento y estructura de [HC[CH(SiMe ((3)) ((SnMe ((3)))))) ((2))) ((+): un catión sec-alquilo notablemente
Mark Schormann1, Shaun Garratt, David L Hughes
1Wolfson Materials and Catalysis Centre, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
Journal of the American Chemical Society
|September 19, 2002
Resumen
Los investigadores sintetizaron nuevas sales de carbocatión sec-alquilo que contienen estaño, lo que demuestra una notable estabilidad térmica sin superácidos. Estos carbocationes estables inician efectivamente las reacciones de polimerización.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química del carbocatión Química del carbocatión
- La ciencia de los polímeros es la ciencia de los polímeros.
Sus antecedentes:
- Los carbocationes tradicionales a menudo requieren condiciones extremas (superacidos, aniones de coordinación débil) para su aislamiento y estabilidad.
- Los compuestos orgánicos sustituidos por estaño ofrecen propiedades electrónicas únicas que pueden influir en la reactividad química y la estabilidad.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevas sales de carbocatión sec-alquilo aislables y aislables.
- Investigar los efectos estabilizadores de los sustituyentes de estaño en la estabilidad del carbocatión.
- Evaluar el potencial de estos nuevos carbocationes como iniciadores de la polimerización.
Principales métodos:
- Reacción del propeno sustituido por estaño con haluros metálicos (MCl4) en presencia de cloruro de estaño.
- Aislamiento y caracterización de las sales de carbocatión resultantes.
- Cristalografía de rayos X y cálculos de la Teoría Funcional de la Densidad (DFT) para aclarar la estructura y la estabilidad.
- Experimentos de polimerización con isobuteno, isopreno y alfa-metilestireno.
Principales resultados:
- Primer aislamiento de sales de carbocatión sec-alquilo térmicamente estables, [HC{CH(R) SnMe3}2]+M2Cl9- (M = Zr, Hf).
- Estabilidad demostrada sin medios superacídicos o aniones de coordinación débil.
- Los cálculos de DFT y el análisis de la estructura cristalina revelaron la polarización del sustituto Sn y la hiperconjugación como factores clave de estabilización.
- El estaño exhibió un efecto estabilizador significativamente más fuerte que el silicio.
- Los carbocationes demostraron ser iniciadores efectivos para la polimerización del isobuteno, el isopreno y el alfa-metilestireno.
Conclusiones:
- Los sustitutos de estaño imparten una estabilidad significativa e inesperada a los carbocationes sec-alquilo.
- Estos nuevos carbocatios de organotina representan una nueva clase de especies catiónicas estables.
- Su eficacia como iniciadores de la polimerización abre caminos para nuevas estrategias de síntesis de polímeros.
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