Examining the Effects of Monomer and Catalyst Structure on the Mechanism of Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization

Autor:	Robert H. Grubbs, Tzu-Pin Lin, William J. Wolf
Rok vydání:	2019
Předmět:	chemistry.chemical_element General Chemistry ROMP Metallacycle Metathesis Biochemistry Catalysis Ruthenium chemistry.chemical_compound Colloid and Surface Chemistry Monomer chemistry Polymerization Polymer chemistry Ring-opening metathesis polymerisation Norbornene
Zdroj:	Journal of the American Chemical Society. 141:17796-17808
ISSN:	1520-5126 0002-7863
DOI:	10.1021/jacs.9b08835
Popis:	The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a monomer-dependent mechanism for polymerization of norbornene monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating monomers and determining the effect of chelation on the polymerization mechanism. The formation of a chelated metallacycle is enforced by both the steric bulk of the NHC and by the geometry of the monomer, leading to a ground-state stabilization that slows the rate of polymerization and also alters the reactivity of the propagating Ru center toward different monomers in copolymerizations. The results presented here add to the body of mechanistic work for olefin metathesis and may inform the continued design of catalysts for ROMP to access new polymer architectures and materials.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::58fcf30a769500d1713b7b6496c30800 https://doi.org/10.1021/jacs.9b08835 Zobrazit plný text záznamu