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Title: Group 4 indenyl complexes for ethylene polymerisation
Author: Arnold, Thomas Allan Quartermaine
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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The aim of this project has been to develop the field of group 4 indenyl metallocene complexes based upon highly methylated ligands. Previous studies have shown that these compounds can be extremely active ethylene polymerisation catalysts, and, as such, are of both significant academic and commercial interest Chapter One introduces metallocene chemistry, discussing developments within the field and the effects of permethylation on indenyl rings. A synopsis of the rise of the ansa-bridge is provided, in addition to highlights from recent zirconocene chemistry. A feature on olefin polymerisation is included, spanning heterogeneous catalysts, homogeneous metallocenes and post metallocenes, as well immobilised complexes and their supports. Chapter Two charts updates to syntheses of bridged and unbridged permethylindenyl ligands. The developments have allowed for their use as viable industrial procedures. Chapter Three is an account of the group 4 organometallic chemistry of the indenyl ligands from Chapter Two. Four bridged metallocenes, including rac-SBI*ZrCl2 and meso-EBI*Zr(CH2Ph)2, are reported. In addition, six unbridged analogues comprising rac/meso-Ind#2MCl2 (M = Zr, Hf) and rac/meso-Ind#2(CH2Ph)2 are described as well as a half-metallocene. The complexes are characterised by single crystal X-ray diffraction and variable temperature NMR spectroscopy. DFT calculations have been performed, with representations of their optimised geometries and frontier MOs given. Chapter Four describes a reliable, reproducible procedure for immobilising group 4 complexes on the surface of solid supports; in total 19 catalysts are prepared. In addition to SSMAO, two new inorganic supports (LDHMAO and Solid MAO) are utilised. The latter has never previously been described in the academic literature. These catalysts have been characterised by IR, UV/visible and solid-state NMR spectroscopy in addition to SEM imaging. Zr K-edge EXAFS experiments were conducted and exceptionally clear data are reported. Chapter Five investigates the aforementioned complexes as both solution- and slurry-phase ethylene polymerisation catalysts. Numerous parameters are tested including temperature and time dependence and all of the catalysts produce high molecular weight polymer in the range 150-300,000 daltons. The activity of rac SBI*ZrCl2 in solution exceeds 22,500 kgPE/molZr/h/bar, and 7,500 kgPE/molZr/h/bar immobilised on Solid MAO. meso-EBI*Zr(CH2Ph)2 displays double the activity of its dichloride analogue. 1-hexene co polymerisation is carried out as part of a high throughput screening study and activities in excess of 30,000 kgPE/molZr/h/bar are reported. Scale-up polymerisation runs are also disclosed. The resultant polymer has been characterised by GPC, as well as X-ray diffraction, SEM, 13C NMR and IR spectroscopy. Chapter Six provides the experimental details and characterising data for the previous chapters. An Appendix consists of crystal structure data while the Electronic Appendix contains the CIFs, DFT output files and the raw polymerisation data.
Supervisor: O'Hare, Dermot Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Inorganic chemistry ; organometallics ; ethylene polymerisation ; zirconium ; indenyl