双核茂金属催化剂的合成、表征与应用

使用桥连配体锂盐与MCl₄络合, 合成了4个不同结构的双核茂金属化合物μ,μ-(CH₂)₃]{C(H)·(η⁵-C₅H₄)(η⁵-C₁₃H₈)](MCl₂)}₂M=Zr or Ti](4, 5)和μ,μ-(CH₂)₃]{C(H)(η⁵-C₅H₄)(η⁵-C₉H₆)]·(MCl₂)}₂M=Zr or Ti](6, 7), 配体和化合物都经过核磁氢谱(¹H NMR)、 碳谱(¹³C NMR)、 红外光谱(IR)及元素分析等表征, 确认了化学结构. 以甲基铝氧烷(MAO)为助催化剂, 化合物4~7为催化剂催化丙烯聚合, 考察了聚合温度、 乙烯压力、 铝钛或铝锆比对催化剂活性及聚合物分子量的影响. 结果表明, 多亚甲基桥连双核茂金属是高活性乙烯和丙烯聚合催化剂, 乙烯聚合活性最高达到7.5× 10⁶ g PE/(mol Zr·h)(化合物6), 丙烯聚合活性达 10 × 10⁵ g sPP/(mol Zr·h)(化合物4). 所得间规聚丙烯(sPP)的间规度指数(SI, r) 达到90%. 在同样条件下, 双核化合物的催化活性、 聚合物分子量M_w(> 100000)以及分子量分布(MWD>2.5)均比相应的单核化合物高(M_w<70000, MWD≤2), 表明该体系中存在较强的核效应.

Synthesis of Methylene-bridged Binuclear Metallocene Complexes and Application for Propylene Syndiospecific Polymerization†

In order to investigate the differences between binuclear metallocene catalysts and mononuclear catalysts for propylene syndiotactic polymerization, binuclear metallocene complexes μ,μ-(CH₂)₃]·{C(H)(η⁵-C₅H₄)(η⁵-C₁₃H₈)](MCl₂)}₂M=Zr or Ti](4, 5), and μ,μ-(CH₂)₃]·{C(H)(η⁵-C₅H₄)·(η⁵-C₉H₆)](MCl₂)}₂M=Zr or Ti](6, 7) were synthesized and characterized by ¹H NMR, ¹³C NMR, mass spectra and elemental analysis. When combined with methylaluminoxane(MAO), these metallocene complexes shown high catalytic activity for the polymerization of ethylene and propylene, the activity of polyethylene(PE) reaches up to 7.5×10⁶ g PE/(mol Zr·h)(complex 6) and 10×10⁵ g sPP/(mol Zr·h)(complex 4) for polypropylene(PP). The syndiotacticity index(SI) of polypropylene(sPP) by complex 4 was more than 90%. It is found that, under the same conditions, binuclear complexes’ catalytic activity, M_w(>100000) and molecular weight distribution(MWD>2.5) are higher than that of corresponding mononuclear metallocene complexes(M_w<70000, MWD≤2), which suggests that there are cooperation effect in binuclear system.