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Synthesis and Application of Ethylene Polymerization Catalysts Bearing [P,O] Backbone or [ONX] Tridentate Ligand

Author: WanDaWei
Tutor: TangYong
School: Suzhou University
Course: Organic Chemistry
Keywords: transition metal polymerization catalysts solution polymerization
CLC: O643.36
Type: PhD thesis
Year: 2012
Downloads: 96
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Abstract


This thesis focuses mainly on the synthesis and application of ethylenepolymerization catalysts bearing [P, O] and [ONX] ligands. The electronic density andstructure of or aroud the centre metal was modulated by ligand backbone, so thebehaviour of polymeriztion or copolymerization was consequently changed.In the first part, a series of β-keto phosphporus ylide with alkoxy groups weresynthesised. Complex77was prepared by oxidative addition of the β-keto phosphporus（V） ylide to Ni（COD）2（COD=1,5-bis（cyclooctadine）） with a migration of aryl group.Typical chemical shift of hygrogen in the chelate [P, O] backbone was5.3ppm. The31PNMR analysis of the complexes showed a typical AB signal at around20ppm due toP-P coupling. Molecular structure confirmed a distorted square planar geometry aroundnickel. The distance between Ni and O2is shorter than the sum of Ni and O van derWaals raddi, indicating a weak interaction between O2and Ni atoms. The distance ofNi-O2decreased in the order of OMe （2.985A,44b）>OEt （2.963A,44c）> O（CH2）4CH3（2.904A,44d）> OiPr （2.871A,44e）, suggestting a gradually stronger O2…Niinteraction in the complexes with increasing of the steric hinderance. In the presence ofNi（COD）2,44a showed an activity of1.03×104g/mol·h·atm toward ethylenepolymerization under10atm of ethylene,60oC,1hour. While44b with methoxyexhibited the activity of7.27×104g/mol·h·atm, which is six times higher than44a.Other catalysts with alkoxyl substituent all gived higher activities than44a. The activityof44e with isopropyl was21.04×104g/mol·h·atm,20times of44a. Polyethylene wasgenerally linear with terminal double bonds characterized by high temperature1H NMRand13C NMR. The alkoxyl was proved to prolong the life of catalysts after ethyleneflowmeter traced the polymerization.44e sustained235minutes while44a only49minutes. The position of the substituent did not affect the activity obviously.For the second part, titanium complexes [ONX]TiCl3were directly synthesised by the corresponding ligand to TiCl4. The donor group of–OPh,-PPh2,-PPh2=Ocoordinated to the centre metal. Their activities were high upon the activation ofMMAO, noticeably,78f sustain3.37×106g/mol·h·atm under temperature of up to130oC. The sidearm increased the activity in the order of—PPh2>-PPh2=O>-SPh>-OPh.78f were active for copolymerization of ethylene with α-olefins （1-hexene,1-decene） or norbornene in the condition of Al/Ti=500and amount of norborene is20mmol. Under the temperature of up to110oC, these catalysts copolymerized ethylenewith1-octene and1-octadecene. Incorpration is5.9%at the amount of80mmolcalculated by13C NMR. Different catalysts were active between0.05-1.89×106g/mol·h·atm. Tm decreased with the incorpration ratio determined by DSC.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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