154283-78-0Relevant articles and documents
Structure-stereospecificity relationships of propylene polymerization using substituted ansa-silylene(fluorenyl)(amido) titanium complexes
Tanaka, Ryo,Yanase, Chie,Cai, Zhengguo,Nakayama, Yuushou,Shiono, Takeshi
, p. 95 - 100 (2016)
ansa-Fluorenylamidotitanium complexes bearing various substituents on the nitrogen and fluorene (2a-d) were synthesized. The structures of the complexes were characterized by 1H and 13C NMR, and X-ray crystal analyses were performed for complexes 2a, 2b and 2d. The coordination mode of the fluorenyl group to the metal center was changed from η3 to η1 when a bulky group was introduced on the nitrogen or 2,3-position of the fluorenyl ring. Syndiotactic-specificity of the catalyst for the propylene polymerization was reduced when bulky group was introduced on the nitrogen. Least-square fitting analysis of the steric pentad distributions revealed that the stereodefect was mainly formed by the chain migration without monomer insertion, which is accelerated by the η1-coordination of the fluorenyl group.
Silylene-bridged fluorenyl-containing ligands and zirconium complexes with C1 and Cs symmetry: general synthesis and olefin polymerization catalysis
Chen, You-Xian,Rausch, Marvin D.,Chien, James C. W.
, p. 1 - 10 (1995)
A variety of new silylene-bridged fluorenyl-containing ligands has been synthesized with good yields via a convenient synthetic route.Two dimethylsilylene-bridged (η5-indenyl)(η5-fluorenyl) (1) and (η5-cyclopentadienyl)(η5-fluorenyl) (2) zirconocene dichlorides with C1 and Cs molecular symmetry have also been prepared.Upon activation with methyl aluminoxane, the former produced a polypropylene of high molecular weight, but with low activity and isotacticity.The latter catalyzed non-stereospecific propylene polymerization without any zyndiotactic tendency, but with 40 and 20 times greater ethylene and propylene activity respectively than the former catalytic system.Keywords: Zirconium; Olefin; Polymerization catalysis; Fluorenyl ligands
The effect that 6-tert-butoxyhexyl functionalization has on ethylene polymerization in ansa-zirconocene dichlorides
Lee, Hyosun,Lee, Choong Hoon
, p. 214 - 223 (2004)
Ethylene polymerization studies have been carried out with novel precatalysts of the type: [(η5-C13 H8)-X(t-BuOC6H12)Me-(η5- C5H4)]ZrCl2 [X=C [1a], Si [2a]], [(η5-C13H8)-XMe2- (η5-(t-BuOC6H12C5 H3))] ZrCl2 [X=C [3a], Si [4a]] in the presence of excess methylalumoxane (MAO) to compare their catalytic activity and to delineate the effect of the 6-t-butoxyhexyl functionality on ethylene polymerization. The precatalysts [1a] and [2a] with the bridge functionality showed higher activity in ethylene polymerization than the corresponding complexes [3a] and [4a] which have it on the Cp ring moiety. On the other hand the silyl bridged complexes [2a] and [4a] produced a higher molecular weight polyethylene than the carbon-bridged one, regardless of the location of functional group.
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.
