ISSN:
0570-0833
Keywords:
Ziegler-Natta catalysts
;
Catalysis
;
Polymerization
;
Polyethylene
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Cp2TiCl2 and Cp2TiEtCl (Cp = cyclopentadienyl, Et = ethyl), in combination with aluminum alkyls, have been studied as model catalyst systems for the polymerization of ethylene in toluene. The activity of these systems resides in the presence of a complex molecule involving an alkylated Ti(IV) and an alkylated Al species, linked together by chlorine bridge bonds. The environment of the Ti is of octahedral symmetry with one vacant site available for the coordination of ethylene. The bridged Al-alkyl causes a destabilization of the Ti-alkyl bond (“trans effect”), thus rendering it active for polymerization. The reduction Ti(IV) → Ti(III), inevitable in these systems, involves the irreversible change from octahedral to tetrahedral symmetry with loss of the catalytic activity. Polymerization and reduction are supposed to occur at the same catalyst site. Magnetic methods (susceptibility and EPR) as well as the kinetics of polymerization were used in the investigation of these catalyst systems.
Additional Material:
15 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/anie.196707901
