Video Experimental Relacionado

Updated: Jun 12, 2026

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Published on: November 29, 2018

Estudio multimodal de interacciones secundarias en complejos Cp*Ir de imidazolilfosfinas que llevan un grupo NH

Douglas B Grotjahn¹, John E Kraus, Hani Amouri

¹Department of Chemistry and Biochemistry, 5500 Campanile Drive, San Diego State University, San Diego, California 92182-1030, USA. grotjahn@chemistry.sdsu.edu

Journal of the American Chemical Society

|May 22, 2010

Resumen

Este estudio explora la unión de hidrógeno en complejos de iridio con ligandos de imidazolilfosfina. Los investigadores encontraron una unión de hidrógeno más fuerte con el cloruro que con el hidrógeno en los complejos de cloruro de hidrógeno, lo que afecta las tasas de reacción y las estructuras complejas.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Química supramolecular de las moléculas.
La espectroscopia y la difracción.

Sus antecedentes:

El enlace de hidrógeno juega un papel crucial en las reacciones químicas y el reconocimiento molecular.
Los ligandos de la imidazolilfosfina ofrecen propiedades electrónicas y estéricas únicas para la química de coordinación.
Comprender los efectos de los ligandos en la estructura y la reactividad de los complejos metálicos es esencial.

Objetivo del estudio:

Para investigar los fenómenos de enlace de hidrógeno en nuevos complejos de iridio con ligandos de imidazolilfosfina.
Para dilucidar la influencia de los sustituyentes de ligando en la estructura compleja, la dinámica y la actividad catalítica.
Para comparar las preferencias de enlace de hidrógeno en diferentes complejos de iridio con varios ligandos.

Principales métodos:

Síntesis y caracterización de complejos de iridio con los ligandos de la imidazolilfosfina (R(2) PImH).
Se emplearon la difracción de rayos X, la resonancia magnética nuclear (RMN) y la espectroscopia infrarroja (IR).
Los cálculos de la Teoría Funcional de Densidad (DFT) y el etiquetado isotópico ((15) N) se utilizaron para el análisis detallado.

Principales resultados:

Los complejos de dicloros exhibieron enlaces de hidrógeno intramoleculares, confirmados por estructuras de rayos X y datos espectroscópicos.
Los complejos de cloruro de hidrógeno mostraron una mayor unión de hidrógeno al cloruro que al hidrógeno.
Se observaron diferencias en la conformación y la dinámica complejas basadas en los sustituyentes de fósforo (isopropilo vs. tert-butilo), reveladas por la espectroscopia de RMN (15) N.

Conclusiones:

Los sustituyentes de ligando influyen significativamente en la estructura, la dinámica y las características de enlace de hidrógeno de los complejos de iridio.
El estudio pone de relieve los desafíos en la caracterización de complejos hemilabílicos, bifuncionales.
Los ligandos de la imidazolilfosfina pueden modular la actividad catalítica, como lo demuestra una modesta mejora en la hidrogenación de transferencia.

Más Videos Relacionados

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Published on: May 28, 2014

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Published on: March 20, 2014

Videos de Conceptos Relacionados

ortho–para-Directing Activators: –CH3, –OH, –&NoBreak;NH2, –OCH3

ortho–para-Directing Activators: –CH₃, –OH, –⁠NH₂, –OCH₃

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

¹H NMR: Complex Splitting

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...

¹H NMR: Long-Range Coupling

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.

Chirality at Nitrogen, Phosphorus, and Sulfur

Chirality at Nitrogen, Phosphorus, and Sulfur

Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...

Regioselectivity and Stereochemistry of Hydroboration

Regioselectivity and Stereochemistry of Hydroboration

A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.