Rare-Earth-Metal–Hydrocarbyl Complexes Bearing Linked Cyclopentadienyl or Fluorenyl Ligands: Synthesis, Catalyzed Styrene Polymerization, and Structure–Reactivity Relationship
作者：Zhongbao Jian ,Dongmei Cui and Zhaomin Hou
关键字：cyclopentadienyl ligands, hydrocarbyl complexes, ligand effects, polymerization, rare-earth metals
论文来源：期刊
具体来源：http://onlinelibrary.wiley.com/wol1/doi/10.1002/chem.201102682/full
发表时间：2012年
A series of rare-earth-metal–hydrocarbyl complexes bearing N-type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized.Treatment of [Y(CH2SiMe3)3(thf)2] with equimolar amount of the electron-donating aminophenyl-Cp ligand C5Me4H-C6H4-o-NMe2 afforded the corresponding binuclear monoalkyl complex [({C5Me4-C6H4-o-NMe(μ-CH2)}Y{CH2SiMe3})2](1?a) via alkyl abstraction and C-H activation of the NMe2 group.The lutetium bis(allyl) complex [(C5Me4-C6H4-o-NMe2)Lu(η3-C3H5)2] (2?b), which contained an electron-donating aminophenyl-Cp ligand, was isolated from the sequential metathesis reactions of LuCl3 with (C5Me4-C6H4-o-NMe2)Li (1?equiv) and C3H5MgCl (2?equiv). Following a similar procedure, the yttrium- and scandium–bis(allyl) complexes, [(C5Me4-C5H4N)Ln(η3-C3H5)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 (C13H9-C5H4N) by [Ln(CH2SiMe3)(thf)2] generated the rare-earth-metal–dialkyl complexes, [(η3-C13H8-C5H4N)Ln(CH2SiMe3)2(thf)] (Ln=Y (4?a), Sc (4?b), Lu (4?c)), in which an unusual asymmetric η3-allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium–trisalkyl complex [Y(CH2C6H4-o-NMe2)3],the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η3-C13H8-C5H4N)Y(CH2C6H4-o-NMe2)2] (5). Complexes1–5 were fully characterized by 1H and 13C?NMR and X-ray spectroscopy, and by elemental analysis. In the presence of both [Ph3C][B(C6F5)4] and AliBu3, the electron-donating aminophenyl-Cp-based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph3C][B(C6F5)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 (4and 5) in combination with [Ph3C][B(C6F5)4] and AliBu3 displayed
much-lower activity to afford syndiotactic-enriched polystyrene.
