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Rare-Earth-Metal-Hydrocarbyl Complexes Bearing Linked Cyclopentadienyl or Fluorenyl Ligands: Synthesis, Catalyzed Styrene Polymerization, and Structure-Reactivity Relationship.
MedLine Citation:
PMID:  22282393     Owner:  NLM     Status:  Publisher    
A series of rare-earth-metal-hydrocarbyl complexes bearing N-type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized. Treatment of [Y(CH(2) SiMe(3) )(3) (thf)(2) ] with equimolar amount of the electron-donating aminophenyl-Cp ligand C(5) Me(4) H-C(6) H(4) -o-NMe(2) afforded the corresponding binuclear monoalkyl complex [({C(5) Me(4) -C(6) H(4) -o-NMe(μ-CH(2) )}Y{CH(2) SiMe(3) })(2) ] (1 a) via alkyl abstraction and CH activation of the NMe(2) group. The lutetium bis(allyl) complex [(C(5) Me(4) -C(6) H(4) -o-NMe(2) )Lu(η(3) -C(3) H(5) )(2) ] (2 b), which contained an electron-donating aminophenyl-Cp ligand, was isolated from the sequential metathesis reactions of LuCl(3) with (C(5) Me(4) -C(6) H(4) -o-NMe(2) )Li (1 equiv) and C(3) H(5) MgCl (2 equiv). Following a similar procedure, the yttrium- and scandium-bis(allyl) complexes, [(C(5) Me(4) -C(5) H(4) N)Ln(η(3) -C(3) H(5) )(2) ] (Ln=Y (3 a), Sc (3 b)), which also contained electron-withdrawing pyridyl-Cp ligands, were also obtained selectively. Deprotonation of the bulky pyridyl-Flu ligand (C(13) H(9) -C(5) H(4) N) by [Ln(CH(2) SiMe(3) )(3) (thf)(2) ] generated the rare-earth-metal-dialkyl complexes, [(η(3) -C(13) H(8) -C(5) H(4) N)Ln(CH(2) SiMe(3) )(2) (thf)] (Ln=Y (4 a), Sc (4 b), Lu (4 c)), in which an unusual asymmetric η(3) -allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium-trisalkyl complex [Y(CH(2) C(6) H(4) -o-NMe(2) )(3) ], the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η(3) -C(13) H(8) -C(5) H(4) N)Y(CH(2) C(6) H(4) -o-NMe(2) )(2) ] (5). Complexes 1-5 were fully characterized by (1) H and (13) C NMR and X-ray spectroscopy, and by elemental analysis. In the presence of both [Ph(3) C][B(C(6) F(5) )(4) ] and AliBu(3) , the electron-donating aminophenyl-Cp-based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph(3) C][B(C(6) F(5) )(4) ] only, the electron-withdrawing pyridyl-Cp-based complexes 3, in particular scandium complex 3 b, exhibited outstanding activitiy to give perfectly syndiotactic (rrrr >99 %) polystyrene, whereas their bulky pyridyl-Flu analogues (4 and 5) in combination with [Ph(3) C][B(C(6) F(5) )(4) ] and AliBu(3) displayed much-lower activity to afford syndiotactic-enriched polystyrene.
Zhongbao Jian; Dongmei Cui; Zhaomin Hou
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-26
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  -     ISSN:  1521-3765     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-1-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (P. R. China), Fax: (+86) 431-526-2774; Graduate School of the Chinese Academy of Sciences, Beijing 100039 (P. R. China).
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