New Chromium(III) Complexes as Highly Active Catalysts for Olefin Polymerization

Enders, Markus; Fernández, Pablo; Ludwig, and Gunter; Pritzkow, Hans

doi:10.1021/om010753+

Cited by 103 publications

(83 citation statements)

References 13 publications

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“…[19] Higher a-olefins are polymerised as well but with much lower catalytic activity. All compounds need a co-catalyst, which is able to alkylate the metal as well as to abstract an anionic ligand.…”

Section: Polymerisation Resultsmentioning

confidence: 99%

Single‐Site Organochromium Catalysts: Synthesis, Characterisation by Paramagnetic NMR and Olefin Polymerisation

Enders¹

2006

Macromolecular Symposia

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Summary: Chromium(III)-complexes with monoanionic spectator ligands allow the preparation of highly active catalysts for ethylene polymerisation. We summarize the synthesis and NMR-spectroscopic investigations of precatalysts with quinolyl-functionalised Cp-ligands. These complexes have advantageous properties. For spectroscopic investigations the rigidity of the ligand framework helps to identify the species present in solution as fewer conformers are possible. For the application as polymerisation catalysts the high stability of the activated catalyst is important. We obtained meaningful analytical data by paramagnetic NMR, combined with DFTcalculation of the spin-density. These and other investigations lead to the conclusion, that the active species is a cationic chromium(III)alkyl complex. However, at present we have not enough information about the exact structure of this species in the absence of coordinating solvent molecules.

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Section: Polymerisation Resultsmentioning

confidence: 99%

Single‐Site Organochromium Catalysts: Synthesis, Characterisation by Paramagnetic NMR and Olefin Polymerisation

Enders¹

2006

Macromolecular Symposia

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“…[ 8,12 ] In previous works, the catalytic system used to synthesize disentangled UHMWPE was a bis (phenoxyimine) titanium (IV) dichloride catalyst. [ 8,13,14 ] In order to verify the possibility of achieving such "disentangled" UHMWPE with single-site catalysts not based on group (IV) metals, we have chosen to investigate the suitability of a chromium-based system, namely [1-(8-quinolyl)indenyl] chromium (III) dichloride, reported to synthesize HDPE [ 15 ] when activated with methylaluminoxane (MAO). DFT study performed on a similar catalyst structure [ 7 ] has showed that the main chain termination process is the transfer to the trimethylaluminum (TMA).…”

Section: Introductionmentioning

confidence: 99%

A Hemi-metallocene Chromium Catalyst with Trimethylaluminum-Free Methylaluminoxane for the Synthesis of Disentangled Ultra-High Molecular Weight Polyethylene

Romano

Ronca

Rastogi

2014

Macromol. Rapid Commun.

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Recently, it has been shown that by using a single-site catalytic system having titanium as a metallic center, it is possible to tailor the entanglement density in the amorphous region of a semi-crystalline ultra-high molecular weight polyethylene (UHMWPE). This route provides the possibility to make high-modulus, high-strength uniaxially and biaxially drawn tapes and films, without using any solvent during processing. In this publication, it is shown that a single-site catalyst having chromium as metallic center, proposed by Enders and co-workers, can also be tuned to provide control on the entanglement density during synthesis of the UHMWPE. However, to achieve the goal some modifications during the synthesis are required. The synthesized polymers can be processed in the solid state below the equilibrium melting temperature, resulting in uniaxially drawn tapes having tensile strength and modulus greater than 3.5 N/tex and 200 N/tex, respectively. Rheological studies have been performed to follow the increase in entanglement density in melt state with time.

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“…[2] Cationic cyclopentadienide chromium(iii) complexes are important examples of such catalysts and display high olefin polymerization activities at room temperature and under 1 atm of ethylene. [3][4][5][6][7][8] As demonstarted by Theopold and co-workers, neutral chromium(iii) complexes that are coordinatively unsaturated and that feature a CrÀ C alkyl s bond are also catalytically active. [9] A series of recent reports demonstrate that cationic olefin-polymerization catalysts can be combined with alkyl aluminum, alkyl magnesium, and alkyl zinc derivatives to afford ethylene oligomers.…”

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confidence: 99%

A Neutral Chromium(III) Catalyst for the Living “Aufbaureaktion”

Mani

Gabbaı̈

2004

Angew Chem Int Ed

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New Chromium(III) Complexes as Highly Active Catalysts for Olefin Polymerization

Cited by 103 publications

References 13 publications

Single‐Site Organochromium Catalysts: Synthesis, Characterisation by Paramagnetic NMR and Olefin Polymerisation

Single‐Site Organochromium Catalysts: Synthesis, Characterisation by Paramagnetic NMR and Olefin Polymerisation

A Hemi-metallocene Chromium Catalyst with Trimethylaluminum-Free Methylaluminoxane for the Synthesis of Disentangled Ultra-High Molecular Weight Polyethylene

A Neutral Chromium(III) Catalyst for the Living “Aufbaureaktion”

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