Vanadium-Catalyzed Ethylene−Propylene Copolymerization: The Question of the Metal Oxidation State in Ziegler−Natta Polymerization Promoted by (β-diketonate)<sub>3</sub>V
作者:Yinlin Ma、Damien Reardon、Sandro Gambarotta、Glenn Yap、Hayder Zahalka、Catherine Lemay
DOI:10.1021/om9808763
日期:1999.7.1
[(acac)2Al(THF)2][Al Cl4] (5). Two unprecedented V(II) complexes (R-acac)2V(TMEDA) [R = H(7a), Cy(7b), t-Bu (7c)] have been prepared and reacted with halocarbons to model the reactivation process. The results indicated that the primary role of reactivating substances, commonly employed in the industrial processes, is to reoxidize V(II) to the trivalent state. The reaction formed the catalyst precursor (R-acac)2VCl(TMEDA)
四种不同的(β-二酮酸酯)3 V络合物[β-二酮酸酯= 2,4-戊二酮(acac),2-乙酰环己酮(Cy-acac),2,2,6,6-四甲基-3,5-庚二酮(t -Bu-acac)和1,1,1,5,5,5-六氟-2,4-戊二酮(F-acac)]的制备和测试作为丙烯-乙烯共聚的催化剂,目的是获得更多见识进入活性物种的结构。有关聚合物组成和催化剂活性的数据表明,Al助催化剂的作用之一是引发过渡金属周围的主要配体争夺。尝试分离催化活性物质,得到了配制成[(β-二酮酮)AlCl 2 ] [VCl 2] [(β-二酮酸酯)2 AlCl]}。该物种仅表现出较小的催化活性,是由寄生虫过程(催化剂失活)引起的。通过用THF进行化学降解实验来支持该配方,得到了[V 2 Cl 3(THF)6 ] [AlCl 4 ]和[(acac)2 Al(THF)2 ] [Al Cl 4 ](5)的混合物。两个史无前例的V(II)络合物(R-