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Un mecanismo alterado de hidrólisis para un díester de fosfato complejo metálico
Tim Humphry1, Marcello Forconi, Nicholas H Williams
1Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA.
Journal of the American Chemical Society
|December 12, 2002
Resumen
Los complejos de cobalto dinuclear aceleran dramáticamente la hidrólisis del fosfato de metilo p-nitrofenilo a través de un nuevo mecanismo de adición-eliminación. Los efectos de isótopos cinéticos revelan una fisión significativa de enlaces P-O en el paso limitador de velocidad, que difiere de los diesters sin complejo.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- Mecanismos de reacción Mecanismos de reacción
- Química biomimética es la química biomimética.
Sus antecedentes:
- La hidrólisis del díester de fosfato es crucial en los sistemas biológicos.
- Los complejos de metales dinucleares pueden imitar los sitios activos de las enzimas.
- Comprender los mecanismos de reacción ayuda en el diseño de catalizadores.
Objetivo del estudio:
- Para dilucidar el mecanismo de hidrólisis del fosfato de metilo p-nitrofenilo complejo a un complejo de cobalto dinuclear.
- Para investigar el estado de transición de la reacción de hidrólisis.
- Para comparar el mecanismo con diesters sin complejidad.
Principales métodos:
- Estudios cinéticos de la hidrólisis.
- Medición de los efectos de isótopos cinéticos (KIEs) utilizando isótopos de oxígeno (18O) y nitrógeno (15N).
- Comparación de las tasas de hidrólisis para diésteres complejos y no complejos.
Principales resultados:
- El diéster complejo se hidrolizó ~10^11 veces más rápido que el diéster no complejo.
- Un gran inverso 18O KIE para el nucleófilo de hidróxido de puente indicó un ataque nucleófilo en el paso de predeterminación de la velocidad.
- Los grandes KIEs de 18O y 15N para el grupo de salida de nitrofenilo indicaron una fisión significativa de los enlaces de éster P-O en la etapa de determinación de la velocidad.
Conclusiones:
- La hidrólisis del diéster complejo procede a través de un mecanismo de adición-eliminación, distinto del mecanismo concertado de los diésteres no complejos.
- El paso de limitación de velocidad implica la expulsión del grupo de salida de p-nitrofenilo de un intermediario.
- El estado de transición para la hidrólisis de diéster complejo exhibe una extensa fisión de enlaces P-O.
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