University of Warwick institutional repository: http://go.warwick.ac.uk/wrap A Thesis Submitted for the Degree of PhD at the University of Warwick http://go.warwick.ac.uk/wrap/2542 This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. A STUDY OF SOME NOVEL CATIONIC COMPLEXES OF THE GROUP 4 METALS AND THEIR APPLICATIONS IN ZIEGLER-NATTA CATALYSIS. Mark L. Butcher A thesis submittedfor the degreeof Doctor of Philosophy. Department of Chemistry University of Warwick February 1994 M1 ii Contents. Chapter 1: Introduction. 1. 1.1 The titanium hafnium. 2. chemistry of zirconium and . 1.2 The Group 4 halides. 4. 1.3 The Group 4. 7. organometallicchemistry of . 1.4 Cyclopentadienylcomplexes of Group 4. 13. 1.5 Cationiccomplexes of Group4. 26. 1.6 Antimony(v) chloride.. 34. Chapter 2: Results and discussion.. 39. 2.1 Preparation of the CpMC13series. 40. 2.2 Preparation of the Cp*MC13species. 43. 2.3 HalideAbstraction from CpTiC13. 45. 2.4 Halide Abstraction from Cp*TiC13. 61. 2.5 Halide Abstraction from CpMC13(MeCN)2for M= Zr and Hf. 64. 2.6 Halide lAbstraction from Cp*MC13(MeCN)2for M= Zr and Hf. 78. 2.7 HalideAbstraction from CpNbCl4(MeCN). 81. 2.8 Reactionsof the CpMn+ complexes... 85. iii Chapter 3: Experimental. 97. 3.1 General. 98. 3.2 The synthesisof 1,2,3,4,5-pentamethylcyclopentadiene. 99. 3.3 Preparationof sodium cyclopentadienide. 102. 3.4 Preparation of trimethylsilylcyclopentadiene.. 103. 3.5 Preparation of monocyclopentadienylmetal chlorides of Ti, Zr, Hf and Nb. 104. 3.6 Halide abstractionreaction of the CpMC13series. 108. 3.7 Halide Cp*MC13 113. abstractionreactions of the series. 3.8 Halide from CpNbC14(MeCN). 116. abstraction . 3.9 MeCN CpM"+ 117. substitution reactionsof the series. 3.10 Hydrolysis of the CpMn+ series. 120. 3.11 The reactions of [CpTi(MeCN)5][SbCl6]3with inorganic salts. 121. 3.12 The reactions of [CpTi(MeCN)51[SbC1613with lithium methyl. 122. Chapter 4: Introduction to Ziegler-Natta catalysis. 123. 4.1 Historical origins. 124. 4.2 Scope of the reaction.. 125. 4.3 Structure and properties of polyolefins. 126. 4.4 Mechanismsof Ziegler-Natta catalysis. 129. 4.5 Mechanismsof stereochemicalcontrol. 133. 4.6 HomogenousZiegler-Natta catalysis.. 135. iv Chapter 5: Zeigler-Natta Polymerisation over the CpMn+ series. 142. 143. 5.1 Ethene polymerisationcatalysis over the CpM"+ series. 5.2 Catalysis AlEt3. 143. with . 5.3 Catalysis MAO. 145. with . 147. 5.4 Polytheneproperties. 148. 5.5 Experimental aspectsof polymerisation. Chapter 6: Conclusions. 152. 5.1 Summary. 153. 5.2 References. 156. V List of Tables. Table 1.1 The relative sizesof the Group 4 metals. 3. Table 1.2 Properties of the CpMC13 series. 13. Table 1.3 Ionic species prepared via halide abstraction with SbCl5in MeCN solution. 36. Table 2.1 Selectedphysical and spectroscopicdata for the CpMC13 42. series. Table 2.2 Selectedphysical and spectroscopicdata for the Cp*MC13series. 44. Table 2.3 Selectedphysical and spectroscopicdata for the CpTin+series. 46. Table2.4 Selectedbond lengths and angles for [CpTi(MeCN)5][SbCI6]3.. 60. Table 2.5 Selectedphysical and spectroscopicdata for the Cp*Ti"+ 62. series. Table2.6 Selectedphysical and spectroscopic data for CpMn+seriesfor M= Zr Hf. 65. the and . Table 2.7 Elemental compositionsof the various 6SbC15. 67. possibleproducts of CpZrC13(MeCN)2+ . Table 2.8 Selectedbond lengths in the [CpHf(MeCN)6]3+cation. 76. Table 2.9 Selectedbond anglesin the [CpHf(MeCN)6]3+cation. 77. Table2.10 Selectedphysical and spectroscopic properties 79. of the Cp*Mn+ seriesfor M= Zr and Hf. Table 2.11 Selectedphysical and spectroscopicproperties of CpNbC14and CpNbCl4(MeCN). 82. Table 2.12 Selectedphysical and spectroscopicproperties of the productof CpNbC14+ 1OSbC15. 84. vi Table 2.13 Elementalcompositions of the various possible productsof CpNbC14+ SbCl5. 84. Table 2.14 The reactionsof [CpTi(MeCN)S][SbCl6]3 with neutral O-donors. 87. Table 3.1 Drying for 98. agents solvents. Table 3.2 Experimentaldetails of the CpER3syntheses, E= Si, Sn. 104. Table 3.3 Experimentaldetails of the Cp*MC13(MeCN)2syntheses, forM=ZrandHf. 106. Table 3.4 Experimental details of the N-donor substitutionreactions. 117. Table 3.5 Experimentaldetails of the CpM"+ hydrolysisreactions. 120. Table 3.6 Experimental details of the reactionsbetween CpTi3+ inorganic 121. and various salts. Table5.1 The productivityof ethenepolymerisation over CpMC13(MeCN)2 with MAO cocatalyst,for M= Ti, Zr and Hf. 145. Table 5.2 The productivity of ethenepolymerisation over the CpZrn+ serieswith MAO cocatalyst,n=0,1,2 and 3. 147. Table 5.3 The relative quantitiesused in the catalytic experiments. 150. vii a List of Figures. Figure 1.1 Diagrammaticdescription of Zr(CH2Ph)4. 8. Figure 1.2 The structuresof CpMC13for M= Ti and Zr. 15. Figure 1.3 The structure of Cp2MC12. 21. Figure 1.4 The Cp4M for M= Zr Hf. 25. structuresof and . Figure 1.5 Thewalt's structure Of I(CP2Ti(H20))2 0]2+. 30. Figure 1.6 Asian's trimetallic [{CpTi(OMe)2}3O]+ structure. 30. Figure 1.7 Bochmann'spostulated structuresof [(Ind)2TiMe][BPh4]. 33. Figure 1.8 The postulatedintermediate of halide exchange. 37. Figure 1.9 The molecular structure of VC13(NCl).2SbC15. 38. Figure 2.1 Expected structure of CpZrC13(MeCN)2. 41. Figure 2.2 Possiblestructures of the intermediates. 50. Figure 2.3 Molecular model of the postulated(apex-apex) intermediate 53. Figure 2.4 Molecular model of the postulated(edge-edge) intermediate 54. Figure 2.5 Molecular model of the postulated(face-face) intermediate 55. Figure 2.6 The asymmetricunit of [CpTi(MeCN)5][SbCI6]3. 58. Figure 2.7 View of the discrete [CpTi(MeCN)5]3+cation. 59. Figure 2.8 The chemicalshift of the Cp group in the relative configurationsof the [CpMC12(MeCN)3]+and [CpMCI(MeCN)4]2+ for M= Zr Hf. 69. complexes and . Figure 2.9 Variable temperature1H NMR spectraof a mixture of the [CpZrCI2(MeCN)3]+and [CpZrCI(MeCN)4]2+ complexes. 71. Figure 74. 2.10 The asymmetricunit of [CpH«MeCN)6][SbCI6]3. Figure 2.11 View of the discrete [CpH4MeCN)6]3+ cation. 75. Figure 2.12 The geometrical isomersof [{CpZr(MeCN)4}20][SbCI6]4 91. Figure 4.1 The structures of polypropene. 126. Figure 4.2 Mechanismpostulated by Natta. 130. viii Figure 4.3 Mechanismproposed by Cosseeand Arlman.. 131. Figure 4.4 Mechanismproposed by Green and Ivin. 132. Figure 4.5 Agostic active centre proposedby Green. 132. Figure 4.6 Enantiomericforms of a propene-metalmoiety. 133. Figure 4.7 Chiral sites on the surface of a catalyst. 134. Figure 4.8 Shilova's 135. mechanism. Figure 4.9 Insertion isolatedby Eisch. 136. product . Figure 4.10 Reactions of [Cp2TiMe(MeCN)][BPh4]. 137. Figure 4.11 Cihlar's 139. proposed active site. Figure 4.12 The structure of methylaluminoxaneproposed by Kaminsky.140. Figure 4.13 The active centre proposedby Kaminsky. 141. Figure 5.1 The bench-scalepolymerisation reactor. 149. ix Acknowledgements. First and foremost I must thank the uncommonly enthusiasticDr. Gerald Willey who has always offered a smile with his advice. In today's world, academia can only benefit from his approach. I am extremely grateful to a number of people who have contributed directly toward the work reported in this thesis. I have been lucky to work with many members of BP International Limited during the course of my studies. The professional attitudes of Dr. Gordan Downs, Dr. John McNally, Dr. Ramdas and Mr John Graham serve as a model to us all. Similarly, my thanks must go to Prof. Mary McPartlin, Dr. Ian Scowen and Dr Michael Drew for their work on the crystallographic sections of this report. Mrs Claire Walker is the best typist I know of. Funding of the studentshipby both the Scienceand EngineeringResearch Council and BP International Limited is gratefully acknowledged. Finally, this report would not be complete without mention of my family and friends. In Janet,Dave, Tim and Tat I have the best friends anyonecould wish for. This is only bettered by the love and support given by my family: Mum, Claire, Angie and Carol. X Declaration. The work submitted in this thesis is my own and was conducted in the Chemistry Department at the University of Warwick. The X-ray crystallography was performed by Prof. Mary McPartlin, Dr. Ian Scowen (University of North London) and Dr. Michael Drew (University of Reading). The sections involving computer-basedmolecular modelling techniqueswere conductedwith the aid of Dr Ramdas (BP International, Sunbury) and those containing polymerisation studies with the help of Mr. John Graham(BP International, Grangemouth). xi Publications. Cationic titanium(IV) complexes via halide abstraction from CpTiCl3: crystal and molecular structure of [CpTi(MeCN)5][SbCl6]3.2MeCN. GR Willey, ML Butcher, M McPartlin, and IJ Scowen,J. Chem. Soc., Dalton Trans., 1994,305. Halide abstractionreactions of antimony(V) chloride and CpMC13(M = Zr, Hf): crystal and molecular structure of [CpHf(MeCN)61[SbCl613. GR Willey, ML Butcher, M McPartlin, and IJ Scowen,J. Chem. Soc., Dalton Trans., (manuscript in preparation). Xll Abstract. The reactionsbetween antimony(v) chloride and the monocyclopentadienyl metal trichlorides of Group 4 (CpMC13for M= Ti, Zr and Hf) in acetonitrile solution have afforded new hexachloroantimonatesalts. These cationic metal- containing products have been isolated and characterisedusing IR, 1H NMR, elemental analysis, and in two cases, X-ray crystallography. The analogous pentamethylcyclopentadienyl(Cp*) systems have also been investigated, with largely similar results. Depending on the stoichiometry employed in the reaction, the relevant mono-, di- and tri-cationic complexescan be formed via halide exchange.