scholarly journals NMR and EPR trapping of the active species in the ethylene polymerization and trimerization catalyst systems

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
I.E. Soshnikov ◽  
N.V. Semikolenova ◽  
A.A. Antonov ◽  
K.P. Bryliakov ◽  
V.A. Zakharov ◽  
...  
Keyword(s):  
Epr Spectroscopy ◽  
Ethylene Polymerization ◽  
Catalyst Deactivation ◽  
Active Species ◽  
Ion Pair ◽  
Polymerization Catalysts ◽  
Ethylene Trimerization ◽  
Catalyst Systems

AbstractIn this work, previously undetected intermediates of several practically promising catalyst systems for ethylene polymerization and trimerization are discussed. In particular, the activation of ethylene polymerization catalysts (1) LNiCl2 (L = 2,4,6-trimethyl- (N-5,6,7-trihydroquinolin-8-ylidene)phenylamine) with AlEt2Cl and AlMe2Cl, (2) activation of bis(imino)pyridine vanadium(III) chloride L1VIIICl3 (L1 = 2,6-(ArN=CMe)2C5H3N, Ar = 2,6-iPr2C6H3; 2,6-Me2C6H3; 2,4,6-Me3C6H2; 3,5- F2C6H3) with AlMe3/[Ph3C]+[B(C6F5)]4¯ and MAO, and (3) selective ethylene trimerization catalyst (FI)TiCl3 (FI = phenoxyimine ligand with an additional aryl-OCH3 donor) with MAO have been assessed by NMR and EPR spectroscopy. The nature of ion-pair intermediates – the closest precursors of the propagating species – has been established, and the major catalyst deactivation pathways are discussed.

Investigating the Nature of the Active Species in Bis(imino)pyridine Cobalt Ethylene Polymerization Catalysts

2009 ◽  
Vol 28 (20) ◽  
pp. 6003-6013 ◽  
Author(s):  
Igor E. Soshnikov ◽  
Nina V. Semikolenova ◽  
Alexey N. Bushmelev ◽  
Konstantin P. Bryliakov ◽  
Oleg Y. Lyakin ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts

scholarly journals Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Oligoethylenes and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

2021 ◽  
Author(s):  
Ilaria D'Auria ◽  
Zeinab Saki ◽  
Claudio Pellecchia
Keyword(s):  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Variable Content ◽  
Peculiar Behavior ◽  
Number Of Branches

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart's α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e. the number of branches of the produced polyethylenes increases while ethylene pressure increases.

Altering molecular weight distributions: Benzyl–phosphinimide titanium complexes as ethylene polymerization catalysts

2004 ◽  
Vol 82 (8) ◽  
pp. 1304-1313 ◽  
Author(s):  
Emily Hollink ◽  
Pingrong Wei ◽  
Douglas W Stephan
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Subsequent Reaction ◽  
X Ray ◽  
Molecular Weight Distributions ◽  
Polymerization Catalysis ◽  
Weight Distributions ◽  
High Yields

The phosphines and corresponding phosphinimines R2BnPNSiMe3 (R = t-Bu, Cy), p-C6H4(CH2PR2)2 (R = t-Bu (1), Cy (2)), and p-C6H4(CH2PR2NSiMe3)2 (R = t-Bu (3), Cy (4)) were prepared in high yields. Subsequent reaction with Ti precursors afforded (R2BnPN)TiCp*Cl2 (Cp* = η-C5Me5; R = t-Bu (5), Cy (6)), (R2BnPN)TiCpCl2 (Cp = η-C5H5; R = t-Bu (7), Cy (8)), p-C6H4(CH2PR2NTiCp*Cl2)2 (R = t-Bu (9), Cy (10)), and p-C6H4(CH2PR2NTiCpCl2)2 (R = t-Bu (11), Cy (12)). Methylation of the above complexes gave (R2BnPN)TiCp*Me2 (R = t-Bu (13), Cy (14)), (R2BnPN)TiCpMe2 (R = t-Bu (15), Cy (16)), p-C6H4(CH2PR2NTiCp*Me2)2 (R = t-Bu (17), Cy (18)), and p-C6H4(CH2PR2NTiCpMe2)2 (R = t-Bu (19), Cy (20)). The activity of these species as catalyst precursors in ethylene polymerization catalysis was evaluated using Schlenk line and Buchi reactor techniques using activation by methylaluminoxane (MAO) or [Ph3C][B(C6F5)4]. All these catalysts showed good activities and yield polymers with relatively broad molecular weight distributions. The bimodal polymers derived from catalysts generated using MAO are proposed to result from additional active species, possibly as a result of reaction of MAO with the benzylic fragments. X-ray data are reported for 1, 4–8, 10, 12–14, 16, and 18–20.Key words: phosphinimides, polymerization, catalysis, polyethylene, titanium, polymer molecular weight distributions.

Development of new selective ethylene trimerization catalysts based on highly active ethylene polymerization catalysts

2018 ◽  
Vol 303 ◽  
pp. 263-270 ◽  
Author(s):  
S. Ishii ◽  
T. Nakano ◽  
K. Kawamura ◽  
S. Kinoshita ◽  
S. Ichikawa ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Polymerization Catalysts ◽  
Highly Active ◽  
Ethylene Trimerization

scholarly journals Spectroscopic Signature and Structure of Active Sites in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

2021 ◽  
Author(s):  
Anton Ashuiev ◽  
Matthieu Humbert ◽  
David Gajan ◽  
Sebastien Norsic ◽  
Jan Blahut ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ethylene Polymerization ◽  
Active Sites ◽  
Active Species ◽  
Atomic Scale ◽  
Polymerization Catalysts ◽  
Paramagnetic Resonance ◽  
Spectroscopic Signatures ◽  
Electron Paramagnetic ◽  
Ziegler Natta Catalysts

Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler-Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of “active sites” of ZN catalysts in the absence of ethylene, referred to as “dormant active sites”, is elucidated from magnetic resonance experiments, carried out on samples reacted with increasing amounts of BCl<sub>3</sub> so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using EPR and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by DFT calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl<sub>2</sub>-supported Ziegler-Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene, and enables us propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations<br>

Doubly fused N,N,N-Iron Ethylene Polymerization Catalysts appended with Fluoride Substituents; probing catalytic performance via a combined experimental and MLR study

2021 ◽  
Author(s):  
Qiuyue Zhang ◽  
Wenhong Yang ◽  
Zheng Wang ◽  
Gregory A. Solan ◽  
Tongling Liang ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Catalytic Performance ◽  
Chloride Complex ◽  
Polymerization Catalysts

Access to six examples of α,α’-bis(imino)-2,3:5,6-bis(pentamethylene)pyridine-iron(II) chloride complex, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2)}2C5HN] (R1 = Me, R2 = R3 = CH(p-FPh)2 Fe1; R1 = Et, R2 = R3 = CH(p-FPh)2 Fe2; R1 = iPr,...

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