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Formation of a Constrained‐Geometry Ziegler Catalyst System Containing a C 1 Instead of the Usual Si 1 Connection Between the Cyclopentadienyl and Amido Ligand Components
Author(s) -
Duda Lothar,
Erker Gerhard,
Fröhlich Roland,
Zippel Frank
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199808)1998:8<1153::aid-ejic1153>3.0.co;2-r
Subject(s) - fulvene , chemistry , cyclopentadienyl complex , catalysis , deprotonation , ligand (biochemistry) , triethylamine , toluene , yield (engineering) , homogeneous catalysis , agostic interaction , medicinal chemistry , homogeneous , geometry , crystallography , stereochemistry , organic chemistry , metal , thermodynamics , composite material , materials science , biochemistry , receptor , mathematics , ion , physics
6‐Amino‐6‐methylfulvene ( 4 ) is cleanly N ‐acylated by treatment with pivaloylchloride/triethylamine to give the fulvene (C 5 H 4 )=C(CH 3 )NHCOCMe 3 ( 5c ). Treatment of 4 with trimethylchlorosilane similarly yields the mono‐ N ‐silylated fulvene (C 5 H 4 )=C(CH 3 )NHSiMe 3 ( 7 ). Both 5c and 7 are cleanly doubly deprotonated e.g. by treatment with LDA to give ligand systems [(C 5 H 4 )C(=CH 2 )NR]Li 2 [ 8a (R = COCMe 3 ) and 8b (R = SiMe 3 ), respectively]. Their treatment with MCl 4 · 2 THF (M = Ti, Zr) yield the spiro ‐metallocenes [(C 5 H 4 )C(=CH 2 )NR] 2 M ( 9 , 10 ). Complex 10a (M = Zr, R = COCMe 3 ) was characterized by X‐ray diffraction. The reaction of 8a with (Et 2 N) 2 ZrCl 2 in THF gives rise to the formation of [(C 5 H 4 )C(=CH 2 )NCOCMe 3 ]Zr(NEt 2 ) 2 ( 11 ) (70 % isolated), and the reaction of 8b with (Et 2 N) 2 ZrCl 2 yields [(C 5 H 4 )C(=CH 2 )NSiMe 3 ]Zr(NEt 2 ) 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 [(Me 5 C 4 )SiMe 2 NCMe 3 ]ZrCl 2 /MAO “constrained‐geometry” Ziegler catalyst system reveals a similar catalyst activity and performance of this novel type of a C 1 ‐bridged “constrained‐geometry” catalyst as it is exemplified by the [(C 5 H 4 )C(=CH 2 )NSiMe 3 ]ZrX 2 ( 12 )/MAO combination.