Sterically crowded aryloxide compounds of aluminum

Healy, M. D.; Wierda, Derk A.; Barron, Andrew R.

doi:10.1021/om00102a020

Cited by 104 publications

(43 citation statements)

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“…The 13 C NMR measurements were performed using a Bruker Avance 300 MHz spectrometer operating at 75 MHz. The sample temperature was 90 8C.…”

Section: Characterisation Methodsmentioning

confidence: 99%

“…The chemical treatment can be carried out by sterically hindered phenols such as 2,6-di-tert-butyl-4-methylphenol (BHT), which is reported to react with TMA. [13,14] The use of TMA-free MAO for catalyst activation has been recently reported by Busico et al [15] and Carlini et al [16] In the absence of an external chain transfer agent, chain termination in propylene polymerisation with a zirconocene/MAO catalyst system can occur via b-H/b-CH 3 transfer to Zr, b-H transfer to monomer and chain transfer to aluminium. [2,17] To determine the operative termination reactions in olefin polymerisation, it is necessary to analyse M w dependency on the polymerisation conditions, in particular on the monomer pressure.…”

Section: Introductionmentioning

confidence: 99%

“…[2,17] To determine the operative termination reactions in olefin polymerisation, it is necessary to analyse M w dependency on the polymerisation conditions, in particular on the monomer pressure. A deeper understanding of termination reactions can be achieved by end group analysis, because each termination route leads to specific end groups in polymer chains, which can be differentiated by 13 C NMR spectroscopy. Understanding and controlling the termination reactions is the tool to increase the M w of polymers.…”

Section: Introductionmentioning

confidence: 99%

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Zirconocene Propylene Polymerisation: Controlling Termination Reactions

Tynys

Eilertsen

Rytter

2006

Macro Chemistry & Physics

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Summary: Propylene was polymerised at varying trimethylaluminium (TMA) concentration with two metallocenes activated by methylaluminoxane (MAO) in an attempt to better understand the effect of TMA on the activation process, catalyst activity and termination reactions. A chemical treatment of MAO solution with 2,6‐di‐tert‐butyl‐p‐cresol was used to obtain TMA‐free polymerisation conditions. The metallocene precursors under investigation were diphenylmethyl(cyclopentadienyl)(9‐fluorenyl)zirconium dichloride (1) and rac‐dimethylsilylbis(4‐tert‐butyl‐2‐methyl‐cyclopentadienyl)zirconium dichloride (2). Chain transfer to aluminium was the dominating termination route for 1/MAO accompanied with β‐H/β‐CH3 transfer to Zr and β‐H transfer to monomer. It was found that β‐H/β‐CH3 transfer to Zr was favoured over the β‐H transfer to monomer at elevated temperatures, and that polymerisation and β‐H transfer to monomer depended on the same critical reaction. For 2/MAO the detected termination routes were β‐H transfer to Zr and chain transfer to aluminium. A strong activity dependency on TMA concentration was observed. With 1/MAO high TMA concentration decreased and stabilised the activity, whereas TMA free polymerisation conditions at 40 °C increased markedly the activity, indicating that TMA coordinated to the active site of 1/MAO. Surprisingly, with more sterically hindered 2/MAO, high TMA concentration increased the activity and nearly complete activity loss occurred at TMA‐free polymerisation conditions at 40 °C.Metallocene precursors for investigation of propylene polymerisation.magnified imageMetallocene precursors for investigation of propylene polymerisation.

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“…The 13 C NMR measurements were performed using a Bruker Avance 300 MHz spectrometer operating at 75 MHz. The sample temperature was 90 8C.…”

Section: Characterisation Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Zirconocene Propylene Polymerisation: Controlling Termination Reactions

Tynys

Eilertsen

Rytter

2006

Macro Chemistry & Physics

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“…Diboraanthracene 3 has been prepared and disclosed independently by Marks et al [8] Herein we report the methide abstraction reactions of 1 with organozirconium compounds and a comparative assessment of B(C 6 F 5 ) 3 and diboranes 1 ± 3 as olefin polymerization initiators. In addition, we describe the behavior of these various activators in the presence of MeAl(BHT) 2 (MAD; BHT 2,6-di-tert-butyl-4-methylphenoxide), a monomeric alkylaluminum compound [9] which appears to be an example of a ªnoninteractingº scrubbing agent of use in olefin polymerization. [10] To assess the solution and solid-state structure of the anion formed upon methide abstraction by 1, we employed the trisamido zirconium complex [MeZr{N(SiMe 3 ) 2 } 3 ]…”

mentioning

confidence: 99%

Activation of [Cp2ZrMe2] with New Perfluoroaryl Diboranes: Solution Chemistry and Ethylene Polymerization Behavior in the Presence of MeAl(BHT)2

Williams

Dai

et al. 1999

Angew. Chem. Int. Ed.

106

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Reversible C(6)F(5) transfer takes place between the boron centers in the anion formed by methide abstraction from [MeZr{N(SiMe(3))(2)}(3)] or [Cp(2)ZrMe(2)] (L(n)M-CH(3) in the reaction scheme) by the perfluorinated diborane 1. The solution chemistry of the metallocenium ion pairs formed from 1 and [Cp(2)ZrMe(2)] is correlated with the observed ethylene polymerization behavior of 1 in comparison to the monoborane B(C(6)F(5))(3), the related diborane 1,2-C(6)H(4)[B(C(6)F(5))(2)](2), and the 9,10-diboraanthracene compound 9,10-(C(6)F(5))(2)C(12)B(2)F(8).

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“…22,[28][29][30][31][32][33][34] It is only with sufficiently sterically bulky ligands precluding dimerization, such as in BHT, the monomeric 3-coordinated Al species are formed. 12,26,27,[35][36][37] We suggested that these well-known compounds possessing high Lewis acidity could be effective activators of metallocene complexes although they were never tested for the purpose. Dimethylated zirconocene was chosen as precatalysts due to seemingly low alkylating ability of isobutylaluminum aryloxides.…”

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confidence: 99%

Isobutylaluminum aryloxides as metallocene activators in Homo‐ and copolymerization of olefins

Faingol’d

Bravaya

Панин

et al. 2015

J of Applied Polymer Sci

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The article describes that sterically hindered isobutylaluminum aryloxides with bulky t Bu substituents at 2,6-positions of aryl fragment, i.e. (2,6-di-Bu (1-TTBP)) and (2,6-di-Me(2-BHT)) can serve as cocatalysts for metallocene complexes. Isobutylaluminum aryloxides have been applied for activation of rac-Et(2-MeInd) 2 ZrMe 2 in homopolymerization of ethylene, propylene, copolymerization of ethylene and propylene, and terpolymerization of ethylene, propylene, and 5-ethylidene-2-norbornene at Al/Zr 5 300 mol/mol. The type of R substituent at 4-position has a significant effect on catalyst activity. The catalytic system with 1-TTBP showed the highest activity in all homo-and copolymerization processes. Diisobutylaluminum aryloxides provide much higher activity to the systems in all polymerization processes and stronger ability for propylene incorporation in copolymer than diaryloxides. The activities of the systems with isobutylaluminum aryloxides are similar or exceed that of the system with MAO as activator as have shown for propylene polymerization.

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Sterically crowded aryloxide compounds of aluminum

Cited by 104 publications

References 0 publications

Zirconocene Propylene Polymerisation: Controlling Termination Reactions

Zirconocene Propylene Polymerisation: Controlling Termination Reactions

Activation of [Cp2ZrMe2] with New Perfluoroaryl Diboranes: Solution Chemistry and Ethylene Polymerization Behavior in the Presence of MeAl(BHT)2

Isobutylaluminum aryloxides as metallocene activators in Homo‐ and copolymerization of olefins

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