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La polimerización asistida nucleofílicamente y con apertura de anillo catiónico de los ferrocenofanos [1] puentes de
Thomas Baumgartner1, Frieder Jäkle, Ron Rulkens
1Department of Chemistry, University of Toronto, 80 St. George Street, Ontario, M5S 3H6, Canada.
Journal of the American Chemical Society
|August 22, 2002
Resumen
Estudios detallados revelan nuevos mecanismos para la polimerización de apertura de anillos (ROP, por sus siglas en inglés) de los ferrocenofanos [1] puentes de estaño. Se identificaron vías nucleófilas y catiónicas, lo que sugiere que las impurezas inician la ROP espontánea.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los ferrocenofanos [1] puentes de estaño exhiben una polimerización espontánea de apertura de anillo (ROP) a temperatura ambiente.
- Comprender los mecanismos de este ROP es crucial para controlar la polimerización y desarrollar nuevos materiales.
Objetivo del estudio:
- Para dilucidar las vías mecanicistas de la ROP espontánea de los ferrocenofanos [1] puentes de estaño.
- Investigar la influencia de varios aditivos en el proceso de polimerización.
- Proponer nuevas metodologías y mecanismos de ROP.
Principales métodos:
- Estudios detallados de la fase de solución de los ferrocenofanos [1] puentes de estaño (R = t-Bu, Mes).
- Investigación de los efectos de diversos aditivos: radicales, nucleófilos (neutrales y aniónicos), ácidos de Lewis, especies protóticas y electrófilos catiónicos.
- Análisis cinético de las tasas de polimerización en condiciones variables.
Principales resultados:
- Se propuso un mecanismo de ROP asistido nucleofílicamente, acelerado por nucleófilos de aminas como la piridina.
- Se observó un proceso de ROP catiónico tras la adición de especies electrófilas (H+, Bu3Sn+).
- Es probable que la ROP espontánea sea iniciada por trazas de impurezas básicas o ácidas de Lewis.
Conclusiones:
- Se han identificado dos nuevos mecanismos de ROP para los ferrocenofanos estirados [1]: nucleofílicos asistidos y catiónicos.
- Estos mecanismos ofrecen nuevas vías para la polimerización controlada de los ferrocenofanos.
- Los hallazgos tienen implicaciones más amplias para la ROP de los metallocenofanos y los metaciclos que contienen elementos del grupo 14.
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