Highly active and stereoselective olefin polymerization catalysts generated by the transfer-epimetallation of olefins or acetylenes with dialkyltitanium(IV) complexes: three-membered metallocycles as active catalyst sites‡

Autor:	Adetenu A. Adeosun, John N. Gitua, Peter O. Otieno, John J. Eisch
Rok vydání:	2004
Předmět:	Olefin fiber Polymers and Plastics Nitrile biology Organic Chemistry Active site Crystal structure Metallacycle Condensed Matter Physics Catalysis chemistry.chemical_compound chemistry Acetylene Polymerization Polymer chemistry Materials Chemistry biology.protein
Zdroj:	Macromolecular Symposia. 213:187-198
ISSN:	1521-3900 1022-1360
DOI:	10.1002/masy.200450918
Popis:	Efficient transfer-epimetallations of simple olefins and acetylenes by R 2 TiL 2 reagents (R = Bu n , Bu 1 ; L = X) are readily achieved in THF at -78°C to generate titanacyclopropa(e)ne intermediates, readily capable of inserting various unsaturated addends (olefin, acetylene, nitrile). Analogous epimetallations conducted in hydrocarbons lead to the isotactic stereoselective polymerization of 1-alkenes and the cyclotrimerization of acetylenes. In place of the widely accepted Arlman-Cossee model for the active catalytic site, namely a Ti-C bond on the TiCl 3 crystal lattice, the 2-substituted-l-halotitanacyclopropyl cation formed in hydrocarbon media is proposed as the active site for stereoselective olefin polymerization.
Databáze:	OpenAIRE
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