| The work discussed in this thesis involves two different projects. The first project consisted of detailed NMR studies of Ti(CH2Ph) 4/B(C6F5)3 and Ti(CH2Ph) 4/[Ph3C][B(C6F5)4] catalyst systems and their catalytic activities in olefin polymerizations. The second project involved low temperature NMR and kinetics studies of β-elimination from dialkyl hafnocene compounds Cp2HfMeR (R = CH2CMe 3, i-Bu) reacting with B(C6F5)3 or [Ph3C][B(C6F5)4]. These two projects are discussed separately as Parts I and II in Chapter Two: Experimental, and Chapter Three: Result and Discussion.; The reaction of Ti(CH2Ph)4 with B(C6F 5)3 resulted in the formation of [Ti(CH2Ph) 3][(η6-PhCH2)B(C6F5) 3], while reactions with [Ph3C][B(C6F5) 4] gave either [Ti(CH2Ph)3][B(C6F 5)4] or [(CH2Ph)3Ti-μ-CH2PhTi(CH 2Ph)3][B(C6F5)4], depending on the Ti(CH2Ph)4:[Ph3C] ratio. NMR evidence was presented that all of these compounds, including Ti(CH2Ph) 4, exhibited multihapto Ti-CH2Ph bonding. The Ti(CH 2Ph)4/B(C6F5)3 and Ti(CH 2Ph)4/[Ph3C][B(C6F5) 4] systems were assessed for their abilities to induce polymerization of ethylene, 1-hexene, isobutylene and ethyl vinyl ether, and the Ti(CH 2Ph)4/[Ph3C][B(C6F5) 4] system was found to be able to function as both a Ziegler-Natta catalyst and a carbocationic initiator.; In the second project, a series of dialkyl hafnocene compounds Cp ′2HfMeR (Cp′ = Cp, Cp*; R = Me, CH2CMe3, i-Bu) was synthesized. The variable temperature kinetics studies of the reversible β-methyl elimination reaction of Cp 2Hf(CH2CMe3(μ-Me)B(C6F5) 3 to give Cp2HfMe(μ-Me)B(C6F5) 3 and isobutylene are also presented in this thesis. The reaction was found to be first-order in Cp2Hf(CH2CMe3(μ-Me)B(C 6F5)3, but was inhibited by Lewis bases which can coordinate preferentially to give complexes of the type [Cp2Hf(L)CH 2CMe3][BMe(C6F5)3] (L = Lewis base, such as diethyl ether). The activation data are shown to be pertinent to the process of β-methyl migration accompanied by the solvent-assisted dissociation of the [BMe(C6F5)3]− anion from the metal. The low temperature NMR studies of Cp 2HfMe(CH2CHMe3)/[Ph3C][B(C6F 5)4] are shown to form methyl-bridged dihafnium compound [(Cp2Hf(CH2CMe3))2(μ-Me)] +-[B(C6F5)4]− as the major product, independent of the Cp2HfMe(CH 2CHMe3):[Ph3C][B(C6F5) 4] ratio. This dihafnium compound preceded an irreversible and consecutive β-methyl elimination at temperatures higher than −20°C in C6D 5Cl. That Cp2HfMe(i-Bu)/B(C6F5<... |
