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Ethylene polymerization by alkylidene‐bridged asymmetric dinuclear titanocene/MAO systems
Author(s) -
Lin Feng,
Sun Junquan,
Liu Xijie,
Lang Wuke,
Xiao Xiaohui
Publication year - 2006
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.23923
Subject(s) - methylaluminoxane , dilithium , ethylene , catalysis , polymer chemistry , polymerization , molar mass distribution , chemistry , polyethylene , molar ratio , coordination polymerization , crystallography , medicinal chemistry , solution polymerization , metallocene , polymer , organic chemistry , ion , deprotonation
Two asymmetric alkylidene‐bridged dinuclear titanocenium complexes (CpTiCl 2 ) 2 (η 5 ‐η 5 ‐C 9 H 6 (CH 2 ) n C 5 H 4 ), 1 ( n = 3) and 2 ( n = 4) have been prepared by treating two equivalents of CpTiCl 3 with the corresponding dilithium salts of the ligands C 9 H 7 (CH 2 ) n C 5 H 5 ( n = 3, 4). Additionally, Ti(η 5 :η 5 ‐ n ‐BuC 5 H 4 C 5 H 5 )Cl 2 (3) and Ti(η 5 :η 5 ‐ n ‐BuC 9 H 6 C 5 H 5 )Cl 2 (4) were synthesized as corresponding mononuclear complexes. All complexes were characterized by 1 H, 13 C NMR, and IR spectroscopy. Homogenous ethylene polymerization catalyzation using those complexes has been conducted in the presence of methylaluminoxane (MAO). The influences of reaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results showed that the catalytic activities of both dinuclear titanocenes were higher than those of the corresponding mononuclear titanocenes. Although the two dinuclear complexes were different in only one [CH 2 ] unit, the catalytic activity of 2 was about 50% higher than that of 1; however, the molecular weight of polyethylene (PE) obtained by 2 was lower than that obtained from 1. The molecular weight distribution of PE produced by these dinuclear complexes reached 6.9 and 7.3, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3317–3323, 2006