Video Experimental Relacionado
Updated: May 4, 2026
06:31
Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
6.4K
Isomerización de alqueno Z-selectivo por complejos de cobalto de alto espín (II)
Chi Chen1, Thomas R Dugan, William W Brennessel
1Department of Chemistry, University of Rochester , 120 Trustee Road, Rochester, New York 14627, United States.
Journal of the American Chemical Society
|January 7, 2014
Resumen
Los investigadores desarrollaron catalizadores de cobalto (II) que isomerizan selectivamente alquenos simples a isómeros Z menos estables. Este avance ofrece un nuevo método para controlar la estereoquímica en la síntesis de alquenos.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis es la catálisis.
- Síntesis estereoselectiva de síntesis.
Sus antecedentes:
- La isomerización de alquenos generalmente favorece a los E-isómeros más estables.
- La síntesis selectiva de Z-alquenos es un reto debido a las preferencias termodinámicas.
Objetivo del estudio:
- Desarrollar un sistema catalítico para la formación selectiva de Z-alqueno mediante isomerización.
- Para dilucidar el mecanismo de la isomerización de alquenos catalizados por cobalto.
Principales métodos:
- Utilizado cobalto ((II) catalizadores con ligandos β-diketiminato voluminosos.
- Empleó experimentos de etiquetado isotópico para estudiar los intermediarios de reacción.
- Desarrolló un modelo estérico para explicar la estereoselectividad.
Principales resultados:
- Se logró la isomerización selectiva de 1-alquenos a Z-2-alquenos.
- Identificó un complejo alquilo de cobalto ((II) de tres coordenadas como el estado de reposo.
- Eficacia demostrada del catalizador con varios sustratos incluyendo silanos y éteres.
Conclusiones:
- Los catalizadores de cobalto (II) con ligandos voluminosos permiten el control cinético para la síntesis de Z-alqueno.
- El mecanismo implica la eliminación rápida del β-hidruro y los pasos de inserción [1,2].
- Los factores estéricos en el estado de transición dictan la estereoselectividad Z.
Videos de Conceptos Relacionados
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
14.2K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
14.2K
02:43E1 Reaction: Stereochemistry and Regiochemistry
9.4K
One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
9.4K
03:02Colors and Magnetism
12.1K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
12.1K
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
2.4K
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
2.4K
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
2.6K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
2.6K
02:52Stereoisomerism
11.1K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
11.1K