Video Experimental Relacionado
Updated: Jul 19, 2026
08:50
Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces
Published on: September 26, 2014
Complejos octaédricos de benzamidinato del grupo 4: síntesis, estructuras y actividades catalíticas en la
Victoria Volkis1, Elza Nelkenbaum, Anatoli Lisovskii
1Department of Chemistry, Institute of Catalysis Science and Technology, Technion, Israel Institute of Technology, Haifa 32000, Israel.
Journal of the American Chemical Society
|February 20, 2003
Resumen
Los complejos de benzamidinato de los metales del grupo 4 catalizan la polimerización del propileno, con la presión que controla la táctica del polímero de atáctico a isotáctico. La estructura del catalizador y el cocatalizador influyen significativamente en la actividad y la estereoregularidad.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- La catálisis es la catálisis.
Sus antecedentes:
- Los ligandos de benzamidinato ofrecen propiedades estéricas y electrónicas sintonizables para la síntesis de complejos metálicos.
- Los complejos metálicos del grupo 4 son ampliamente explorados como catalizadores para la polimerización de olefinas.
Objetivo del estudio:
- Para sintetizar y caracterizar los ligandos de benzamidinato y los complejos metálicos del grupo 4.
- Investigar la actividad catalítica de estos complejos en la polimerización del propileno.
- Comprender cómo las condiciones de reacción y la estructura compleja afectan a la microestructura del polímero.
Principales métodos:
- Estudios de síntesis y difracción de rayos X de complejos de benzamidinato.
- Experimentos de polimerización del propileno con el uso de cocatalizadores MAO o B ((C ((6) F ((5)) ((3)).
- Análisis de la microestructura del polímero (tacticidad, estereoregularidad) en función de los parámetros de reacción.
Principales resultados:
- Se sintetizaron complejos octaédricos de benzamidinato de Zr y Ti.
- La actividad del catalizador y la estereoregularidad fueron moduladas por la presión, el disolvente y el cocatalizador.
- El complejo 9 con B ((C ((6) F ((5)))) dio polipropileno altamente isotáctico (98% mmmm).
- El Complejo 10 produjo polipropileno elastomérico a alta presión.
- Los elastómeros exhibieron dominios isotácticos alternos y estereodefectos debido a la epimerización.
Conclusiones:
- Los complejos de benzamidinato son catalizadores versátiles para la polimerización estereorregulada del propileno.
- La presión es un parámetro clave para controlar la táctica del polímero.
- La estructura compleja y la elección del cocatalizador son fundamentales para lograr las propiedades deseadas del polímero.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:15Carboxylic Acid Derivatives: Overview
Carboxylic acid derivatives are formed by replacing the hydroxyl group of carboxylic acids with a different functional group. The most common carboxylic acid derivatives are:
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
01:07Preparation of Acid Anhydrides
One of the methods for preparing symmetrical or unsymmetrical acid anhydrides involves the treatment of acid chlorides with the sodium salt of carboxylic acids. The reaction proceeds via a nucleophilic acyl substitution.
The carboxylate ion acts as a nucleophile that attacks the carbonyl carbon of the acid chloride to form a tetrahedral intermediate. Subsequently, the re-formation of the carbonyl group with the loss of the chloride ion as a leaving group leads to the formation of an acid...
The carboxylate ion acts as a nucleophile that attacks the carbonyl carbon of the acid chloride to form a tetrahedral intermediate. Subsequently, the re-formation of the carbonyl group with the loss of the chloride ion as a leaving group leads to the formation of an acid...
01:13Five-Membered Heterocyclic Aromatic Compounds: Overview
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.
01:14Polymer Classification: Architecture
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
01:26Polymer Classification: Stereospecificity
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...