Cationic Tropidinyl Scandium Catalyst: A Perfectly Acceptable Substitute for Cationic Half-Sandwich Scandium Catalysts in cis-1,4-Polymerization of Isoprene and Copolymerization with Norbornene

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• 作者：Siqian Liu ; Gaixia Du ; Jianyun He ; Yingyun Long ; Shaowen Zhang ; Xiaofang Li
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：June 10, 2014
• 年：2014
• 卷：47
• 期：11
• 页码：3567-3573
• 全文大小：303K
• 年卷期：v.47,no.11(June 10, 2014)
• ISSN：1520-5835

文摘

Different nonmetallocene rare earth metal alkyl complexes such as monotropidinyl (Trop) scandium dialkyl complex (Trop)Sc(CH₂SiMe₃)₂(THF) (1), ditropidinyl yttrium alkyl complex (Trop)₂Y(CH₂SiMe₃)(THF) (3) as well as binuclear lutetium alkyl complex bearing one tetradentate dianionic 6-N-methyl-1,4-cycloheptadienyl (NMCH) ligand [(NMCH)Lu(CH₂SiMe₃)(THF)]₂ (2) have been synthesized in high yields via one-pot acid鈥揵ase reaction by using of the tris(trimethylsilylmethyl) rare earth metal complexes with the readily available natural product tropidine. The polymerization experiments indicate that the monotropidinyl scandium dialkyl complex 1 displays reactivity akin to that of the analogous monocyclopentadienyl scandium dialkyl complexes. In the presence of activator and a small amount of AlMe₃, complex 1 exhibits similar activities (up to 1.6 脳 10⁶ g mol_Sc^鈥? h^鈥?) but higher cis-1,4-selectivities (up to 100%) than (C₅H₅)Sc(CH₂SiMe₃)₂(THF) (cis-1,4-selectivity as 95%) in the isoprene polymerization, yielding the pure cis-1,4-PIPs with moderate molecular weights (M_n = 0.5鈥?1.2 脳 10⁴ g/mol) and bimodal molecular weight distributions (M_w/M_n = 1.48鈥?.07). Moreover, the complex 1/[Ph₃C][B(C₆F₅)₄/AlⁱBu₃ ternary system also shows good comonomer incorporation ability in the copolymerization of isoprene and norbornene similar to the [C₅Me₄(SiMe₃)]Sc(畏³-CH₂CHCH₂)₂/activator binary system, affording the random isoprene/norbornene copolymers with a wide range of isoprene contents around 57鈥?1 mol % containing cis-1,4 configuration up to 88%.