联苯基桥连双核茂锆化合物的合成及催化乙烯聚合

4,4′-二溴联苯与n-BuLi反应得到对-联苯基二锂,再与四甲基环戊烯酮进行羰基加成,酸催化脱水,一步得到对-联苯基桥连四甲基环戊二烯配体4-(C₅Me₄H)C₆H₄-C₆H₄(C₅Me₄H)-4(1).配体1相继与n-BuLi和ZrCl₄反应得到相应的联苯基桥连双(单茂三氯化锆)4-(C₅Me₄ZrCl₃)C₆H₄-C₆H₄(C₅Me₄ZrCl₃)-4,不经分离直接与环戊二烯基锂或茚基锂反应得到相应的双核锆化合物4-(C₅MeZrCl₂Cp′)C₆H₄-C₆H₄·(C₅Me₄ZrCl₂Cp′)-4[Cp′=C₅H₅(2),C₉H₇(3)].研究了在MAO(MethylAluminoxane)助催化下,化合物2和3对乙烯聚合的催化性能.化合物2和3都显示了非常高的催化活性,并在较高的温度下达到最高活性.

Synthesis and Application in Ethylene Polymerization of p-Biphenylene-bridged Dinuclear Zirconocenes

?Dibromobiphenyl reacted with n-BuLi to form 4,4′-dilithiobiphenyl, which further reacted with 2,3,4,5-tetramethylcyclopent-2-enone following the elimination of water to give the ligand 4-(C₅Me₄H)C₆H₄-C₆H₄(C₅Me₄H)-4(1). Ligand 1 reacted with n-BuLi and ZrCl₄ to form the p-biphenylene-bridged dinuclear tetramethylcyclopentadienyl zirconium trichlorides 4-(C₅Me₄ZrCl₃)·C₆H₄-C₆H₄(C₅Me₄ZrCl₃)-4, which reacted in situ with cyclopentadienyl lithium(CpLi) or indenyl lithium(IndLi) to give the corresponding p-biphenylene-bridged dinuclear zirconocenes 4-(C₅Me₄ZrCl₂Cp′)C₆H₄-C₆H₄(C₅Me₄ZrCl₂Cp′)-4 [Cp′= Cp(2), Ind(3)]. The zirconocenes 2 and 3 were characterized by ¹H NMR, MS spectra and elemental analysis, and were studied for ethylene polymerization with methyl aluminoxane(MAO) as cocatalyst. Both 3 and 4 show very high activities and reach the maximum at a higher temperature, indicating that the introduction of the p-biphenylene-bridge increased the catalytic activity and thermal stability of the dinuclear zirconocene catalysts.