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UBC Theses and Dissertations

Practical and green design strategies for the catalytic synthesis of functional materials Gilmour, Damon John


The use of early transition metal complexes bearing N,O-chelating ligands for the preparation of functional materials is described within. The two central reactions explored are the hydroaminoalkylation of alkenes and the ring-opening polymerization of cyclic esters. To understand the key features of hydroaminoalkylation towards the design of more efficient catalysts, computational investigations using DFT have been used to develop a theoretical model of the catalytic cycle. The use of a sterically bulky, electron withdrawing amidate ligand leads to the formation of electrophilic metal centres that possess a plane of favorable reactivity trans to the amidate ligand. The steric bulk of the amidate ligand lowers the energy barrier to form catalytically active tantallaziridine species; however, it may also relieve steric congestion by accessing κ¹ bonding modes throughout the catalytic cycle. In the computed cycle, protonolysis of the 5-membered metallacycle is the turnover-limiting step and points toward a key area for optimizing reactivity through catalyst design. N,O-chelating pyridonate ligands are used with tantalum to form highly active hydroaminoalkylation catalysts for the challenging alkylation of cyclic diene substrates. The resulting amino-norbornene and amino-cyclooctene products are then polymerized using ring-opening metathesis polymerization to prepare polyolefins containing pendant amine groups. The viscoelastic characterization of these materials is conducted by melt rheology and reveals profound and surprising physical properties that result from the association of polymer chains by dynamic hydrogen-bonding. Reduction of the polymer backbone gives saturated polymers to yield pendant amine-functionalized polyethylene analogs. These materials show interesting physical properties, including self-healing and adhesion to poly(tetrafluoroethylene). Titanium pyridonates are used to conduct the ring-opening polymerization of cyclic esters. The modification of the ligand environment through changing the number of pyridonates or the nature of the nucleophilic ligand does not dramatically affect the resulting polymers obtained. These initiators are also used to combine rac-lactide and ε-caprolactone into random and block copolymers. A stoichiometric reaction with methylene lactide and the ruthenium starting material RuCl₂(PPh₃)₃ is used to prepare a novel ring-opened ruthenium carboxylate species. This product results from the nucleophilic attack of a liberated triphenylphosphine ligand from the starting complex.

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