132686-51-2Relevant academic research and scientific papers
Preparation and crystal structures of the complexes (η5-C5H4CPh2-η5-C13H8)MCl2 (M = Zr, Hf) and the catalytic formation of high molecular weight high tacticity syndiotactic polypropylene
Razavi, Abbas,Atwood, Jerry L.
, p. 117 - 124 (1993)
The reaction of MCl4 (M=Zr, Hf) with the dilithium salt of 1-cyclolopentadienyl-1-fluorenyl-1,1-diphenylmethane in pentane at ambient temperature leads to the formation of the complexes (η5-C5H4CPh2-η5-C13H8)MCl2.NMR and X-ray diffra
In Situ Activation: Chances and Limitations to Form Ultrahigh Molecular Weight Syndiotactic Polypropylene with Metallocene Dichlorides
Stieglitz, Lucas,Henschel, Daniel,Pehl, Thomas,Rieger, Bernhard
, p. 4055 - 4065 (2021/09/30)
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.
Bridged asymmetric dinuclear metallocene compounds, and preparation and application thereof
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Paragraph 0111; 0135, (2017/07/22)
The invention provides bridged asymmetric dinuclear metallocene compounds, and preparation and application thereof. The compounds have the structure disclosed as Formula I, wherein R1s and R2s are selected from C1-C5 alkyl or phenyl, and are different; optionally, the two R1s or two R2s can independently form a naphthene base with the carbon atom connected with the R1 or R2; and R3 and R4 are selected from hydrogen, C1-C8 alkyl, bromine or chlorine. The bridged asymmetric dinuclear metallocene compounds for sPP have the advantages of simple synthesis route, high product yield and easy separation and purification; and when being used for catalyzing propylene polymerization, the bridged asymmetric dinuclear metallocene compounds have the advantages of low cocatalyst consumption, high catalytic activity and high polymer syndiotacticity.
