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Deciphering the Olefin Isomerization-Polymerization Paradox of Palladium(II) Diimine Catalysts: Discovery of Simultaneous and Independent Pathways of Olefin Isomerization and Living Polymerization.
Nguyen, Dung; Wang, Shengguang; Grabow, Lars C; Harth, Eva.
Afiliação
  • Nguyen D; Department of Chemistry, Center of Excellence in Polymer Chemistry (CEPC), University of Houston, 3589 Cullen Boulevard, Houston, Texas 77204, United States.
  • Wang S; Williams A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, 4226 Martin Luther King Blvd, Houston, Texas 77204, United States.
  • Grabow LC; Center for Programmable Energy Catalysis (CPEC), University of Minnesota, 421 Washington Ave., SE, Minneapolis, Minnesota 55455, United States.
  • Harth E; Williams A. Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, 4226 Martin Luther King Blvd, Houston, Texas 77204, United States.
J Am Chem Soc ; 145(17): 9755-9770, 2023 May 03.
Article em En | MEDLINE | ID: mdl-37071817
This work elucidates a long-standing unexplained paradox commonly observed within the polymerization of α-olefin using palladium (Pd)(II)-diimine catalysts, in which isomerization and living polymerization of α-olefins are both observed. With a classical mechanistic understanding of these complexes, this behavior is often dismissed and interpreted as experimental error. Herein, we present a comprehensive mechanistic investigation into this phenomenon that supports the existence of a novel mechanistic pathway for Pd(II)-diimine complexes. Part one of the mechanistic study lays the foundation of the proposed mechanism, in which neutral Pd(II)-diimine complexes were found to exhibit a moderate to good catalytic activity for olefin isomerization of α-olefins despite the established notion that catalyst activation is required. Extensive experimental and computational studies reveal the possibility of a partial dissociation of the diimine ligand, which frees up one coordination site and enables coordination-insertion. This finding is significant as the coexistence of two reactive coordination sites at the palladium center becomes a valid proposal for the activated cationic Pd(II)-diimine complexes. In part two, we examined and validated the simultaneously observed α-olefin isomerization and living polymerization using the cationic Pd(II)-diimine catalyst, which supports the presence of two independent reaction pathways of isomerization and polymerization, respectively. Moreover, the addition of a strong Lewis acid, such as AlCl3, accelerates the ligand dissociation and the consequential isomerization as it weakens the palladium-nitrogen bond through competitive binding. In part three, Lewis acid-triggered olefin isomerization-polymerization is employed to prepare living olefinic block copolymers and further synthesize novel polyolefin-polar block copolymers with unique architectures, distinct levels of branching, crystallinity, and polar functionality in a one-pot manner.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Am Chem Soc Ano de publicação: 2023 Tipo de documento: Article País de afiliação: Estados Unidos País de publicação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Am Chem Soc Ano de publicação: 2023 Tipo de documento: Article País de afiliação: Estados Unidos País de publicação: Estados Unidos