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In Situ Activation: Chances and Limitations to Form Ultrahigh Molecular Weight Syndiotactic Polypropylene with Metallocene Dichlorides
Organometallics ( IF 2.5 ) Pub Date : 2021-09-13 , DOI: 10.1021/acs.organomet.1c00397 Lucas Stieglitz 1 , Daniel Henschel 1 , Thomas Pehl 1 , Bernhard Rieger 1
Organometallics ( IF 2.5 ) Pub Date : 2021-09-13 , DOI: 10.1021/acs.organomet.1c00397 Lucas Stieglitz 1 , Daniel Henschel 1 , Thomas Pehl 1 , Bernhard Rieger 1
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Fluorenyl cyclopentadienyl Cs-symmetric ansa-metallocene (M = Zr, Hf) complexes I–IV featuring different bridging motifs (C and Si) were synthesized and subsequently examined in the syndiospecific coordinative polymerization of propylene. All complexes were activated in situ with triisobutylaluminum (TIBA) and [Ph3C][B(C6F5)4] (TrBCF) in order to highlight the benefits of this in situ activation, resulting in a significantly higher molecular weight and a significantly increased productivity in comparison to methylaluminoxane (MAO). The isopropylidene-bridged zirconocene Ia (ZrCl2[Me2C(η5-Flu)(η5-Cp)]) exhibited a high productivity (80000 kgPP (molcat h)−1) and stereoregularity ([rrrr] up to 93%) with a moderate molecular weight of polypropylene (PP), whereas the polymerization with the corresponding hafnocene Ib (HfCl2[Me2C(η5-Flu)(η5-Cp)]) resulted in a lower productivity and stereoregularity but yielded ultrahigh molecular weight polypropylene (Mw = 1100 kg mol–1). The backbone in II (HfCl2[Ph2C(η5-Flu)(η5-Cp)]) was associated with a higher productivity and molecular weight, while the syndiotacticity was not affected. In contrast, SC-XRD revealed a reduced dihedral angle and D value for Si-bridged hafnocenes III (HfCl2[Me2Si(η5-Flu)(η5-Cp)]) and IV (HfCl2[Ph2Si(η5-Flu)(η5-Cp)]), resulting in a more constrained geometry of the catalyst. This led to an increased molecular weight, while the productivity as well as the syndiotacticity decreased due to these structural parameters. Activation of Ib and II–IV with n-octyl-modified methylaluminoxane (MMAO) resulted in a lower molecular weight of the polymer, because the transfer of the growing polymer chain onto the Al center was enhanced. Nevertheless, the stereoregularity of MMAO-activated catalysts was slightly increased, probably due to a coordination of the ill-defined MMAO anion during the polymerization. DSC analysis exposed for syndiotactic polypropylene (sPP) produced by the highly active zirconocene Ia a defined melting transition (Tm up to 145.2 °C), whereas TIBA/TrBCF-activated hafnocenes Ib and II–IV gave polymers with no observable Tm value.
中文翻译：
原位活化：用茂金属二氯化物形成超高分子量间规聚丙烯的机会和限制
合成了具有不同桥接基序（C 和 Si）的芴基环戊二烯基C s对称柄型茂金属（M = Zr，Hf）配合物I - IV，随后在丙烯的间规配位聚合中进行了检测。所有复合物活化原位用三异丁基铝（TIBA）和[PH 3 C] [B（C 6 ˚F 5）4，以突出的这样的好处（TrBCF）原位活化，导致与甲基铝氧烷 (MAO) 相比显着更高的分子量和显着提高的生产率。异丙叉桥联的二茂锆Ia (ZrCl 2 [Me 2 C(η 5 -Flu)(η 5 -Cp)]) 表现出高生产率 (80000 kg PP (mol cat h) -1 ) 和立构规整性 ([rrrr] up至 93%) 与中等分子量的聚丙烯 (PP)，而与相应的铪茂Ib (HfCl 2 [Me 2 C(η 5 -Flu)(η 5-Cp)]) 导致较低的生产率和立构规整性，但产生超高分子量聚丙烯 ( M w = 1100 kg mol –1 )。II (HfCl 2 [Ph 2 C(η 5 -Flu)(η 5 -Cp)]) 中的主链与更高的生产率和分子量相关，而间同立构规整度不受影响。相反，SC-XRD揭示了降低二面角和d为Si的桥连的茂铪值III（的HfCl 2 [我2的Si（η 5 -Flu）（η 5 -Cp）]）和IV（的HfCl 2 [PH2 Si(η 5 -Flu)(η 5 -Cp)])，导致催化剂的几何形状更加受限。这导致分子量增加，而由于这些结构参数，生产率和间同规整度降低。用n激活Ib和II – IV-辛基改性的甲基铝氧烷 (MMAO) 导致聚合物的分子量降低，因为增长的聚合物链向 Al 中心的转移得到增强。然而，MMAO 活化催化剂的立体规整性略有增加，这可能是由于聚合过程中不明确的 MMAO 阴离子的配位。DSC 分析显示由高活性二茂锆Ia产生的间规聚丙烯 (sPP)具有定义的熔融转变（T m高达 145.2 °C），而 TIBA/TrBCF 活化的铪茂Ib和II – IV得到的聚合物没有可观察的T m值.
更新日期：2021-09-13
中文翻译：
原位活化：用茂金属二氯化物形成超高分子量间规聚丙烯的机会和限制
合成了具有不同桥接基序（C 和 Si）的芴基环戊二烯基C s对称柄型茂金属（M = Zr，Hf）配合物I - IV，随后在丙烯的间规配位聚合中进行了检测。所有复合物活化原位用三异丁基铝（TIBA）和[PH 3 C] [B（C 6 ˚F 5）4，以突出的这样的好处（TrBCF）原位活化，导致与甲基铝氧烷 (MAO) 相比显着更高的分子量和显着提高的生产率。异丙叉桥联的二茂锆Ia (ZrCl 2 [Me 2 C(η 5 -Flu)(η 5 -Cp)]) 表现出高生产率 (80000 kg PP (mol cat h) -1 ) 和立构规整性 ([rrrr] up至 93%) 与中等分子量的聚丙烯 (PP)，而与相应的铪茂Ib (HfCl 2 [Me 2 C(η 5 -Flu)(η 5-Cp)]) 导致较低的生产率和立构规整性，但产生超高分子量聚丙烯 ( M w = 1100 kg mol –1 )。II (HfCl 2 [Ph 2 C(η 5 -Flu)(η 5 -Cp)]) 中的主链与更高的生产率和分子量相关，而间同立构规整度不受影响。相反，SC-XRD揭示了降低二面角和d为Si的桥连的茂铪值III（的HfCl 2 [我2的Si（η 5 -Flu）（η 5 -Cp）]）和IV（的HfCl 2 [PH2 Si(η 5 -Flu)(η 5 -Cp)])，导致催化剂的几何形状更加受限。这导致分子量增加，而由于这些结构参数，生产率和间同规整度降低。用n激活Ib和II – IV-辛基改性的甲基铝氧烷 (MMAO) 导致聚合物的分子量降低，因为增长的聚合物链向 Al 中心的转移得到增强。然而，MMAO 活化催化剂的立体规整性略有增加，这可能是由于聚合过程中不明确的 MMAO 阴离子的配位。DSC 分析显示由高活性二茂锆Ia产生的间规聚丙烯 (sPP)具有定义的熔融转变（T m高达 145.2 °C），而 TIBA/TrBCF 活化的铪茂Ib和II – IV得到的聚合物没有可观察的T m值.
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