학술논문
Formation of a Constrained-Geometry Ziegler Catalyst System Containing a C1 Instead of the Usual Si1 Connection Between the Cyclopentadienyl and Amido Ligand Components
Document Type
Article
Source
European Journal of Inorganic Chemistry; August 1998, Vol. 1998 Issue: 8 p1153-1162, 10p
Subject
Language
ISSN
14341948; 10990682
Abstract
6-Amino-6-methylfulvene (4) is cleanly N-acylated by treatment with pivaloylchloride/triethylamine to give the fulvene (C5 H4 )=C(CH3 )NHCOCMe3 (5c). Treatment of 4 with trimethylchlorosilane similarly yields the mono-N-silylated fulvene (C5 H4 )=C(CH3 )NHSiMe3 (7). Both 5c and 7 are cleanly doubly deprotonated e.g. by treatment with LDA to give ligand systems [(C5 H4 )C(=CH2 )NR]Li2 [8a (R = COCMe3 ) and 8b (R = SiMe3 ), respectively]. Their treatment with MCl4 · 2 THF (M = Ti, Zr) yield the spiro-metallocenes [(C5 H4 )C(=CH2 )NR]2 M (9, 10). Complex 10a (M = Zr, R = COCMe3 ) was characterized by X-ray diffraction. The reaction of 8a with (Et2 N)2 ZrCl2 in THF gives rise to the formation of [(C5 H4 )C(=CH2 )NCOCMe3 ]Zr(NEt2 )2 (11) (70 % isolated), and the reaction of 8b with (Et2 N)2 ZrCl2 yields [(C5 H4 )C(=CH2 )NSiMe3 ]Zr(NEt2 )2 (12) (76 % isolated). Treatment of complex 12 with an excess of methylalumoxane (MAO) in toluene solution results in the generation of an active homogeneous Ziegler catalyst for the polymerization of ethene. A comparison with the usually employed [(Me5 C4 )SiMe2 NCMe3 ]ZrCl2 /MAO constrained-geometry Ziegler catalyst system reveals a similar catalyst activity and performance of this novel type of a C1 -bridged constrained-geometry catalyst as it is exemplified by the [(C5 H4 )C(=CH2 )NSiMe3 ]ZrX2 (12)/MAO combination.