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The purpose of this research was to synthesize the constrained geometry catalyst Ti[(C5Me4)SiMe2(tBuN)]Cl2 (1) with MAO as a cocatalyst for ethylene homopolymerization and copolymerizations with 1-TMSO-alkenes to produce a copolymer with polar functionality. Three 1-alkenols of varying length were purchased and derivatized and used for the copolymerization experiments: 2-propen-1-ol, 3-buten-1-ol and 9-decen-1-ol. Several variables were tested to determine their effects on comonomer incorporation such as temperature, equivalents of comonomer, equivalents of MAO and two different solvents. Higher catalytic activities were correlated with fewer equivalents of polar comonomer, lower temperatures, and no fewer than 1000 equivalents of MAO. Toluene was found to be a far more effective reaction solvent than dichloromethane, as polymer yields were on average thirteen times higher. All polymer samples were analyzed by high temperature 1H NMR spectroscopy and selected samples were analyzed by DSC and IR spectroscopy. DSC determined that the polyethylene produced by 1 was substantially linear HDPE with long chain branching and that comonomer incorporation reduced the Tc and Tm, probably due to increased short chain branching. 1-TMSO-9-Decene was the most effective comonomer, as it had the highest incorporation rates (8.0 mol%) of all three of the polar comonomers. The two shorter comonomers exhibited no incorporation at all. This confirmed the hypothesis that polar comonomers with longer chains would be less prone to poisoning the electrophilic catalyst. / Thesis (Master, Chemistry) -- Queen's University, 2009-04-27 10:16:46.356

The major goals of this work were to: develop a new methodology for the preparation of site-isolated catalytic sites on a silica surface, prepare the first truly single-site supported metallocene/CGC polymerization catalyst, and develop structure-reactivity relationships for these new systems. To synthesize these novel catalysts, the approach taken was to develop a protocol which allows for the synthesis of an aminosilica material with isolated, uniform amine sites. This patterned aminosilica was then used as a scaffold to support a constrained geometry catalyst. These functionalizations occurred at essentially a quantitative level, in stark contrast to previous literature reports. The patterned catalysts were evaluated in the polymerization of ethylene and compared to densely loaded literature materials. Overall, it was found the patterned materials were 5-10 times more active than traditional immobilized CGC catalysts. The patterned catalysts were also found to be effective catalysts for the copolymerization of norbornenes (including functionalized norbornenes) and ethylene, the first reported use of a tethered CGC for the production of ethylene-norbornene copolymers. The control materials were inactive in these polymerizations, providing further evidence that the patterning protocol allows for the synthesis of unique highly active, isolated catalytic sites. Various structural components of the immobilized CGC developed in this work were tested for their impact on catalyst synthesis and reactivity in ethylene polymerizations. The results showed the patterned materials in general behaved according to the trends seen in homogeneous CGC polymerizations. These results, while congruent with similar homogeneous CGC studies, are in direct conflict with previous work on supported CGCs reported in the literature. This discrepancy is likely the result of the difference between the isolated, possibly single-site patterned catalysts developed in the course of this work and the multi-sited catalysts prepared by traditional supporting protocols. This also further illustrates the difficulty in developing structure-reactivity relationships when ill-defined solid catalysts are used.

Utilization of methylaluminoxane (MAO) activated metallocene and constrained geometry (CGC) olefin polymerization catalysts containing fluorenyl or octamethyloctahydrodibenzofluorenyl (Oct) moieties has yielded three series of syndiotactic copolymers of propylene with higher a-olefins. The melting temperatures of these polymers were analyzed, and found to correspond directly with the mole percent incorporation of comonomer, as well as with the frequency of stereoerrors in the polymers. Further analysis indicated that rmrr stereoerrors, a result of site epimerization, occur in close proximity to the incorporated comonomers. The MAO-activated fluorenyl/Oct-containing metallocene and CGC catalysts were further utilized to produce syndiotactic samples of poly(1-butene) (s-PB) and poly(1- pentene) (s-PPe). The syndiotacticity of the samples was quantified by 13C NMR and the melting temperatures determined by DSC. The samples of s-PB and s-PPe produced by Me2Si( h1-C29H36)( h1-N-tBu)ZrCl2·OEt2 (Oct-CGC) were found to melt at higher temperatures (55.9 and 43.1 °C, respectively) than any previously reported samples. The MAO-activated Oct-CGC was also used to produce polyethylene samples at a variety of polymerization temperatures and pressures. All of the samples were found to contain an unprecedented degree of branching (13-65 total branches per 1000 carbon atoms) for an early transition metal single-site catalyst. The branches were found to be almost exclusively of two or greater than five carbon atoms in length, and the levels of the longer branches could be controlled by varying the polymerization conditions. The number of ethyl branches was roughly 5 per 1000 carbon atoms for all samples. Finally, a binary catalyst system comprising the Oct-CGC and a chromium-based ethylene trimerization catalyst, ((tBuSCH2CH2)2NH)CrCl3, was developed. This MAOactivated catalyst system could be tuned to produce polyethylene samples with 17-49 total branches per 1000 carbon atoms. Between 4 and 16 of these branches were found to arise from incorporation of 1-hexene produced by the chromium oligomerization catalyst. Adjusting the ratios of oligomerization catalyst, polymerization catalyst, and activator was found to allow rational control over the branch content of the polymers. The branching levels could also be varied by altering the time between injection of the oligomerization and polymerization catalysts into the system.

Group 3 and 4 complexes bearing linked cyclopentadienyl amido ligands, often referred to as constrained geometry complexes (CGCs), have experienced considerable interest due to their superior ability to copolymerise ethylene and higher alpha-olefins when activated with suitable co-catalyst.The work presented in this thesis aimed to replace the most commonly applied bridge in CGCs, which is silicon based, by one containing boron. The potential of the bridging element to have Lewis acidic character was expected to positively alter the catalytic activity of the activated species and possibly allowing for self-activation.Synthetic approaches to ligand precursors based on aminoboranes, diaminodiboranes(4) and ferrocenylboranes are described. Starting from the dihalo derivatives of these boranes, sequential substitution of the halides by one equivalent each of a cyclopentadienide derivative and an amide allowed the synthesis and isolation of a broad range of new CGC ligand precursors.Complexation of these ligand precursors to Group 4 metals was studied by utilising various protocols. The reaction with Group 4 tetraamides via amine elimination was the most successful yielding numerous new boron-bridged CGCs and related complexes in which the boron-bridged ligand binds in a non-chelating fashion.The newly synthesised compounds were fully characterised by multinuclear NMR spectroscopy, supplemented by X-ray diffraction studies where applicable.Studies on the reactivity of boron-bridged CGCs in the presence of alkylating agents indicated susceptibility of the boron atom to nucleophilic attack resulting in a decomposition of the linking moiety between the cyclopentadienyl and amido fragments. This is as well reflected in the data gathered from polymerisation experiments, in which methylaluminoxane activated boron-bridged CGCs displayed a low activity towards ethylene polymerisation, but a high activity towards styrene polymerisation. Such characteristics are comparable to unbridged compounds, e.g. [(eta5-C5H5)TiCl3], rather than silicon-bridged CGCs, thus suggesting degradation of the boron-bridged CGCs to unbridged complexes under polymerisation conditions.