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This thesis describes the synthesis and characterisation of new mononuclear and binuclear zirconium and hafnium compounds containing ansa-bridged ligands. Some olefin polymerization studies, employing the new compounds as catalysts, are also presented. Chapter 1 begins with an introduction to Ziegler-Natta polymerization of olefins, concentrating on recently developed metallocene-based catalyst systems. The second part of the Chapter charts the development of group 4 ansa-metallocene derivatives, especially their use as stereospecific catalysts. Finally, a review of binuciear group 4 metallocene compounds containing bridging bis(cyclopentadienyl)-type ligands is presented. Chapter 2 describes the synthesis and characterisation of some novel mononuclear metallocene compounds of zirconium and hafnium containing ansa-bridged ligands. The ansa-bridged mononuclear compounds [{Me2C(η5-C5H4)(η2-C9H6)}M(η5C5H5)Cl] (M = Zr, Hf), [{(CH2)5C(η5-C5H4)(η2-C9H6)}M(η5-C5H5)Cl] (M = Zr, Hf) and [{Me2(η5-C5H4)(η3-C13H8)}Zr(η5-C5H5)Cl] are described, along with the X-ray crystal structures of the zirconium compounds. The η2-indenyl and η3-fluorenyl coordination modes observed for these compounds are unprecedented. The synthesis and characterisation of the novel, mononuclear ansa-bridged compounds [{Me2C(η5-C5H4)}M(η5-C5H5)Cl] (M = Zr, Hf) is also described, along with their X-ray crystal structures. The variable temperature solid state 13C CP/MAS NMR spectra of [{Me2C(η5-C5H4)}M(η5-C5H5)Cl] (M = Zr, Hf) show slow rotation of the C5H5 ring on the NMR timescale. Chapter 3 describes the synthesis and characterisation of some novel homo- and hetero-binuclear metallocene compounds of zirconium and hafnium in which the metals are bridged by an unsymmetrical ansa ligand. The novel, chiral homobinuclear compounds [(η5-C5H5)MCl2{(η5-C5H4)CMe2(η5-C9H6)}MCl2(η5-C5H5)] (M = Zr, Hf) are described. The ansa-bridged mononuclear compounds [{Me2C(η5-C5H4)(η2-C9H7)M(η5-C5H5)Cl] (M = Zr, Hf) are used as reagents for the selective synthesis of the heterobinuclear analogues [(η5-C5H5)MCl2{(η5-C5H4)CMe2(η5-C9H6)}M*Cl2(η5-C5H5)] (M = Zr, M* = Hf ; M = Hf, M* = Zr) and the unsymmetrical homobinuclear compound [(η5-C5H5)ZrCl2{(η5-C5H4)CMe2(η5-C9H6)}ZrCl2(η5-C5Me5)]. The methylated derivatives [(η5-C5H5)M(CH3)2{(η5-C5H4)CMe2(η5-C5H6)}M*(CH3)2(η5-C5H5)] (M = Zr, M* = Zr, Hf; M = Hf, M* = Zr, Hf) are also described. The structurally related mononuclear compounds [(η5-C5H5)MCl2{(η5-C5H4)CMe2(C9H7)}] (M = Zr, Hf) and [(η5-C5H5)Zr(CH3)2{(η5-C5H4)CMe2(C9H7)}] have also been prepared. Chapter 4 presents some olefin polymerization studies using the new compounds described in Chapter 3 as catalysts, along with either methylaluminoxane or the recently developed co-catalysts [Ph3C]+[B(C6F5)4]- and B(C6F5)3. Chapter 5 provides the experimental details for the reactions described in this thesis and the characterising data for all new compounds are given in Chapter 6 Crystallographic data for the for the X-ray structure determinations in Chapter 2 are given in the Appendices. |
