Effects of Ligand Substitutions on the Rotation Rate of Indenyl Ligands in Bis(2-arylindenyl)zirconocenes by NMR Line-Shape Analysis and Relaxation in the Rotating Frame

Autor:	Gregg M. Wilmes, Marcia B. France, Stephen R. Lynch, Robert M. Waymouth
Rok vydání:	2004
Předmět:	chemistry.chemical_classification Zirconium Chemistry Ligand Organic Chemistry chemistry.chemical_element Polymer Photochemistry Catalysis Inorganic Chemistry Crystallography chemistry.chemical_compound Polymerization Stereoselectivity Physical and Theoretical Chemistry Isomerization Metallocene
Zdroj:	Organometallics. 23:2405-2411
ISSN:	1520-6041 0276-7333
DOI:	10.1021/om034166v
Popis:	Unbridged bis(2-arylindenyl)metallocene complexes, such as bis(2-phenylindenyl)zirconium dichloride (1a), when treated with appropriate activators are active catalyst precursors for the production of elastomeric polypropylene. The proposed mechanism for polymerization involves isomerization of the catalyst between geometries of differing stereoselectivity on a time scale slower than polymer chain growth. As the rotation of the 2-arylindenyl ligand is proposed to result in the different catalyst geometries, the rate at which this rotation occurs is of interest for the interpretation of the behavior of these complexes. A series of zirconocenes {bis(2-phenylindenyl)zirconium dimethyl (1b), bis(2-phenylindenyl)zirconium dibenzyl (1c), bis(2-(3,5-di-tert-butylphenyl)indenyl)zirconium dimethyl (2b), and bis(2-(3,5-di-tert-butylphenyl)indenyl)zirconium dibenzyl (2c)}, varying both in the indenyl ligand framework and the σ-ligand, has been synthesized. The rotation rates of the methyl-substituted metallocenes are...
Databáze:	OpenAIRE
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