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La borilación C ((sp ((2)) -H catalizada por cobalto: conocimientos mecánicos que inspiran el diseño del catalizador
Jennifer V Obligacion1, Scott P Semproni1, Iraklis Pappas1
1Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
Journal of the American Chemical Society
|August 2, 2016
Resumen
Los catalizadores de cobalto con sustituyentes específicos mejoran la eficiencia de la borilación C-H. Esta investigación aclara el mecanismo catalítico, lo que lleva a un diseño mejorado del catalizador para activar arenas no reactivas.
Área de la Ciencia:
- Química organometálica
- Catálisis
- Química sintética
Sus antecedentes:
- Los complejos de cobalto bis (fosfino) piridina (PNP) catalizan la borilación C-H.
- Comprender el mecanismo catalítico es crucial para la optimización del catalizador.
Objetivo del estudio:
- Elucidar el mecanismo de la borilación C-H catalizada por cobalto PNP de la 2,6-lutidina.
- Diseñar y sintetizar catalizadores de cobalto PNP mejorados para una mayor actividad.
Principales métodos:
- Estudios cinéticos (ley de la velocidad, efectos de los isótopos cinéticos)
- Caracterización del catalizador (incluida la cristalografía de rayos X)
- Análisis electroquímico (voltametría cíclica)
Principales resultados:
- La activación de C-H por un intermediario de cobalto (I) borilo limita el volumen de negocios.
- La borilación del catalizador en la posición 4 influye en las tasas de adición oxidativa C-H.
- Los sustituyentes donantes de electrones y estériles en el ligando PNP mejoran la actividad del catalizador.
- Los catalizadores de cobalto optimizados exhiben un cambio en el paso que limita la velocidad a la eliminación reductora de C-B.
- El complejo de iridio correspondiente está inactivo debido a las altas barreras de eliminación reductoras.
Conclusiones:
- La comprensión mecanicista guía el diseño racional del catalizador.
- Los efectos de los sustituyentes en los catalizadores de cobalto PNP tienen un impacto significativo en la eficiencia de la borilación C-H.
- Los catalizadores optimizados permiten una borilación eficiente de los arenes no activados.
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