Designing of imine thiophene-ligated metal-complexes and implication in ethylene polymerization

Designing of imine thiophene-ligated metal-complexes and implication in ethylene polymerization

Polyethylene is the single largest volume polymer produced globally using Ziegler-type catalysts. Numerous modifications have been reported in search of a better catalyst that can control molecular weight, polydispersity, and branching. In our attempts to identify a suitable imine thiophene-ligated...

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Bibliographic Details
Published in:Journal of macromolecular science. Part A, Pure and applied chemistry Vol. 61; no. 11; pp. 874 - 884
Main Authors: Shaikh, Maulali H, Ramekar, Rohan V, Jawoor, Shailaja, Dash, Soumya R, Birajadar, Rajkumar S, Pawal, Sandip B, Thenmani, Nandakumar, Vanka, Kumar, Chikkali, Samir H
Format: Journal Article
Language:English
Published: New York Taylor & Francis 01-11-2024
Marcel Dekker, Inc
Subjects:
Catalysts
Chain branching
Chain transfer
Chromium
Cr-complexes
DFT
High density polyethylenes
high-density polyethylene
Imine thiophene ligand
Infrared spectroscopy
Insertion
Ligands
Molecular weight
NMR
Nuclear magnetic resonance
Polydispersity
Polyethylene
Polymerization
Titanium
Transition metals
Zirconium
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Summary:Polyethylene is the single largest volume polymer produced globally using Ziegler-type catalysts. Numerous modifications have been reported in search of a better catalyst that can control molecular weight, polydispersity, and branching. In our attempts to identify a suitable imine thiophene-ligated chromium complex, we examined 9 different titanium complexes computationally. The DFT investigations considered barriers for insertion, propagation, and termination by β-H elimination or chain transfer, and identified N-(4-methoxyphenyl)-2-phenyl-1-(thiophen-2-yl)ethan-1-imine(L9) as the most suitable ligand. Subsequently, L9 was prepared in good yield (70%) by condensing 2-phenyl-1-(thiophen-2-yl)ethan-1-one with 4-methoxyaniline. Ligand L9 was treated with early transition metal precursors (Ti, Cr, Zr) to generate a homogenous catalyst. The identity of these catalysts was unambiguously ascertained using a combination of NMR, ICP, FT-IR, UV-Vis spectroscopy, and ESI-MS. The performance of L9-ligated titanium complex [Cat.1] was examined in ethylene polymerization using MMAO as a co-catalyst. Insertion of ethylene was tracked using high-pressure NMR experiments and Cat.1 was found to be active in the polymerization. Ethylene polymerization conditions were optimized to obtain high activity and molecular weight polyethylene. The chromium complex [Cat.2] outperformed the Ti and Zr-derived catalysts with the highest TOF of 6294 mol of PE/mol of Cr/h. Cat.2 produced high molecular weight, high-density polyethylene. Rational designing and synthesis of imine thiophene-ligated Ti, Cr, and Zr-complexes and their performance in ethylene polymerization is presented.
ISSN:1060-1325
1520-5738
DOI:10.1080/10601325.2024.2409753