Syndiospecific polymerization of styrene catalyzed in situ by alkoxyl substituted half-sandwich titanocene and BF3·Et2O

Qian, Yanlong; Zhang, Hao; Qian, Xianmiao; Huang, Jiling; Shen, Chen

doi:10.1016/s1381-1169(02)00412-0

Cited by 19 publications

(4 citation statements)

References 40 publications

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“…Nevertheless, we recently found that the difluoride [ rac ‐(ebthi)ZrF 2 ] ( 1 ),6b,c in contrast to the analogous dichloride,6a is an efficient catalyst for ethylene polymerization after activation with i Bu 3 Al (or i Bu 2 AlH) 7a–c. In the literature, there are several empirical reports of TiF and ZrF olefin‐polymerization catalysts 7d–f. To understand these results, we studied the reaction of 1 with two equivalents of i Bu 2 AlH and found that hydride anions replace the fluoride ligands of 1 to give the complex [{ rac ‐(ebthi)ZrH(μ‐H)} 2 ] ( 2 ) (Scheme ) 8a,b.…”

Section: Methodsmentioning

confidence: 99%

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

et al. 2006

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Not a catalyst killer: In the reaction of 2 with B(C6F5)3, a nucleophilic aromatic substitution with CF bond cleavage leads to the unexpected difluoride 1. Although the formation of ZrF species during olefin polymerization by [Cp′2ZrR]+[RB(C6F5)3]− (Cp′=substituted or unsubstituted η5‐cyclopentadienyl; R=Me, H) catalysts is often described as a deactivation, the catalyst precursor 2 can be regenerated from 1 through treatment with iBu2AlH.

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Section: Methodsmentioning

confidence: 99%

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

et al. 2006

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“…Dennoch haben wir kürzlich gefunden, dass das Difluorid [ rac ‐(ebthi)ZrF 2 ] ( 1 )6b,c im Unterschied zum entsprechenden Dichlorid6a nach Aktivierung mit i Bu 3 Al (oder i Bu 2 AlH) einen effizienten Katalysator für die Ethen‐Polymerisation ergibt 7a–c. In der Literatur findet sich des Weiteren eine Reihe empirischer Hinweise auf Ti‐F‐ und Zr‐F‐Katalysatoren für die Olefin‐Polymerisation 7d–f. Um diese Ergebnisse zu verstehen, hatten wir bereits die Reaktion von 1 mit zwei Äquivalenten i Bu 2 AlH untersucht und die Substitution von Fluorid durch Hydrid zum Komplex [{ rac ‐(ebthi)ZrH(μ‐H)} 2 ] ( 2 ) gefunden (Schema ) 8a,b.…”

Section: Methodsunclassified

Die Bildung von Zirconocenfluoriden – keine Desaktivierung in der Olefinpolymerisation mit den Kontaktionenpaar‐Katalysatoren [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

et al. 2006

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Der unerwarteten Bildung von Difluorid 1 bei der Reaktion von 2 mit B(C6F5)3 geht eine nucleophile aromatische Substitution unter C‐F‐Bindungsspaltung voraus. Für den Olefinpolymerisationskatalysator [Cp′2ZrR]+[RB(C6F5)3]− (Cp′=substituiertes oder unsubstituiertes η5‐Cyclopentadienyl; R=Me, H) ist die Entstehung von Zr‐F‐Spezies oft als Desaktivierungsweg beschrieben worden, doch im vorliegenden Fall kann die Katalysatorvorstufe 2 durch die Einwirkung von iBu2AlH auf 1 regeneriert werden.

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“…On the other hand, the bond enthalpies of a Al–X bond differ more significantly (X = Cl 511 kJ mol –1 vs F 663 kJ mol –1 ), suggesting that the resultant Al–F bond-forming step should present a considerable driving force. Indeed, investigations involving metallocene and half-metallocene fluorides in polymerization applications − have revealed some unusual findings, and notably the term “fluoride effect” has been coined. , The disclosure of rac -(ebthi)ZrF 2 / i -Bu 3 Al as an active catalyst system for ethylene polymerization while its chloride analogue is inactive under comparable conditions represents an example of this fluoride effect.…”

Section: Introductionmentioning

confidence: 99%

Active O,N_py,N-Titanium(IV) Fluoride Precatalysts for Ethylene Polymerization: Exploring “Fluoride Effects” on Polymer Properties and Catalytic Performance

et al. 2016

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Three examples of discrete six-coordinate O,N py ,N-bearing titanium(IV) trifluoride complexes, [{2-(C 5 H 4 N)-6-(CMe 2 O)C 5 H 3 N}TiF 3 ] (1), [{2-were prepared using a one-step HF elimination protocol from cis-[(THF) 2 TiF 4 ] and the corresponding pincer ligand precursor (HL1, HL2 H , and HL2 Ph ). A mer configuration of the three fluoride ligands is adopted in their solid-state structures, which is mirrored in solution, as shown by mutual two-bond F−F coupling in their 19 F{ 1 H} NMR spectra. For purposes of comparison, the chloride counterparts of 2a and 3a,, are also reported. On treatment with excess MAO, 1 is scarcely active in ethylene polymerization, 2a is more active, and the most sterically protected system, 3a, represents the most active nonmetallocene metal-fluoride precatalyst reported to date (340 g mmol −1 h −1 bar −1 ) and produces ultra-high-molecular-weight polyethylene (UHMWPE). Similar structure−activity correlations are displayed for chloride-containing 2b and 3b, but, in general, they are significantly more active than their fluoride counterparts, with 3b being the most productive of the series (990 g mmol −1 h −1 bar −1 ). Using fluoride rather than chloride in the precatalyst has a marked effect on not only the molecular weight but also the molecular weight distribution, with broad dispersities (Đ) being a feature of the polymers obtained from 2a and 3a, whereas those for chloride-containing 2b and 3b are appreciably narrower. Single-crystal X-ray structures are reported for 1, 2a, 2b, and 3a.

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Syndiospecific polymerization of styrene catalyzed in situ by alkoxyl substituted half-sandwich titanocene and BF3·Et2O

Cited by 19 publications

References 40 publications

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Die Bildung von Zirconocenfluoriden – keine Desaktivierung in der Olefinpolymerisation mit den Kontaktionenpaar‐Katalysatoren [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Active O,N_py,N-Titanium(IV) Fluoride Precatalysts for Ethylene Polymerization: Exploring “Fluoride Effects” on Polymer Properties and Catalytic Performance

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Syndiospecific polymerization of styrene catalyzed in situ by alkoxyl substituted half-sandwich titanocene and BF3·Et2O

Cited by 19 publications

References 40 publications

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′2ZrR]+[RB(C6F5)3]−

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′2ZrR]+[RB(C6F5)3]−

Die Bildung von Zirconocenfluoriden – keine Desaktivierung in der Olefinpolymerisation mit den Kontaktionenpaar‐Katalysatoren [Cp′2ZrR]+[RB(C6F5)3]−

Active O,Npy,N-Titanium(IV) Fluoride Precatalysts for Ethylene Polymerization: Exploring “Fluoride Effects” on Polymer Properties and Catalytic Performance

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Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact‐Ion‐Pair Catalysts [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Die Bildung von Zirconocenfluoriden – keine Desaktivierung in der Olefinpolymerisation mit den Kontaktionenpaar‐Katalysatoren [Cp′₂ZrR]⁺[RB(C₆F₅)₃]⁻

Active O,N_py,N-Titanium(IV) Fluoride Precatalysts for Ethylene Polymerization: Exploring “Fluoride Effects” on Polymer Properties and Catalytic Performance