Stereospecific polymerization of propylene with group 4 ansa-fluorenylamidodimethyl complexes
作者:Kei Nishii、Hideaki Hagihara、Tomiki Ikeda、Munetaka Akita、Takeshi Shiono
DOI:10.1016/j.jorganchem.2005.08.027
日期:2006.1
Group 4 [eta(1):eta(3)-tert-butyl(dimethylfluorenylsilyl)amido]dimethyl complexes [t-BuNSiMe(2)Flu]MMe2 (M = Ti, 1; Zr, 2; Hf, 3) were synthesized in a one-pot synthesis starting from the ligand, MeLi and MCl4 (M = Ti, Zr, Hf), respectively. The structures of these complexes were determined by X-ray crystallography and the results obtained revealed that the fluorenyl ligand coordinates to center metal in a eta(3)-manner irrespective of center metal employed. Propylene polymerization was conducted at 0 or 20 degrees C in toluene by 1-3 combined with dried methylaluminoxane (MAO), which was prepared from the toluene solutions of MAO by removing free trialkylaluminiums, and HNMe2PhB(C6F5)(4) in the presence of triisobutylaluminium. The 1-dried MAO system gave the polymer with syndiotactic triad (rr) of 63% at 0 degrees C, whereas 2 and 3 did not give any polymer in the same conditions. The 2-dried MAO system gave the polymer with the highest syndiotacticity (rr = 97%) at 20 degrees C, although the activity was low. The 3-dried MAO system did not give any polymer even at 20 degrees C. When HNMe2PhB(C6F5)(4) was used in place of dried MAO at 20 degrees C, 1 gave almost atactic polymer, while 2 and 3 gave highly syndiotactic one (rr > 90%). These results indicate that the catalytic performance strongly depended on the center metal of the ansa-fluorenylamidodimethyl complexes as well as cocatalysts employed. (c) 2005 Elsevier B. V. All rights reserved.