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Complejos heterobimetálicos que contienen enlaces Ca-Fe o Yb-Fe: síntesis y estructuras moleculares y electrónicas de
Matthew P Blake1, Nikolas Kaltsoyannis, Philip Mountford
1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
Journal of the American Chemical Society
|September 6, 2011
Resumen
Las tierras alcalinas pesadas y los metales de tierras raras forman enlaces directos metal-metal con complejos de hierro. Los enlaces itérbio-hierro son más cortos y más fuertes que los enlaces calcio-hierro, lo que difiere de los compuestos de magnesio.
Área de la Ciencia:
- Química organometálica de las sustancias orgánicas.
- Química inorgánica y inorgánica.
- Química del estado sólido.
Sus antecedentes:
- La síntesis y caracterización de nuevos enlaces metal-metal son cruciales para comprender el enlace químico.
- Investigar la reactividad de metales pesados de tierras alcalinas y metales divalentes de tierras raras con compuestos organometálicos proporciona información sobre sus propiedades electrónicas.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos compuestos que presentan enlaces metales-metales directos entre el calcio o el ytterbio y el hierro.
- Para comparar las características de unión y las propiedades estructurales de los enlaces calcio-hierro e iterbio-hierro.
- Investigar la reacción del magnesio con el mismo precursor del hierro y comparar los resultados.
Principales métodos:
- Síntesis de compuestos enlazados metal-metal a través de reacciones de amalgama.
- Difracción de rayos X monocristalino para la determinación estructural.
- Cálculos de la Teoría Funcional de Densidad (DFT), incluidos los análisis de Ziegler-Rauk, el orbital molecular y los átomos en las moléculas.
Principales resultados:
- Se sintetizaron compuestos isostruturales [MFp{2}{THF}{3}}{2} (M = Ca o Yb) con enlaces directos M-Fe (Ca-Fe: 3.0185{6} Å, Yb-Fe: 2.9892{4} Å).
- Los cálculos de DFT confirmaron distancias Yb-Fe más cortas e indicaron un enlace predominantemente electrostático M-Fe.
- Los enlaces Yb-Fe exhibieron una mayor energía de interacción y densidad de electrones en el punto crítico de enlace que los enlaces Ca-Fe.
- El magnesio reaccionó para formar MgFp{2}{THF}{4} sin enlace directo Mg-Fe.
Conclusiones:
- Los enlaces directos metal-metal entre Ca/Yb y hierro son alcanzables, siendo los enlaces Yb-Fe más fuertes y más cortos que los enlaces Ca-Fe.
- El enlace M-Fe es principalmente electrostático, apoyado por análisis computacionales.
- El magnesio exhibe una reactividad diferente, formando complejos O-unidos en lugar de enlaces directos metal-metal.
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