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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 ‡
Author(s) -
Eisch John J.,
Gitua John N.,
Otieno Peter O.,
Adeosun Adetenu A.
Publication year - 2004
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200450918
Subject(s) - olefin fiber , polymerization , acetylene , chemistry , stereoselectivity , catalysis , tacticity , reagent , polymer chemistry , nitrile , organic chemistry , polymer
Abstract Efficient transfer‐epimetallations of simple olefins and acetylenes by R 2 TiL 2 reagents (R = Bu n , Bu t ; 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‐1‐halotitanacyclopropyl cation formed in hydrocarbon media is proposed as the active site for stereoselective olefin polymerization.