Lavoie, GinoFlores Romero, Victor2025-11-112025-11-112025-06-102025-11-11https://hdl.handle.net/10315/43328This dissertation explored the synthesis of Group 4 and Zn catalysts bearing guanidine–phenolate or amidine–phenolate ligands and their ability to catalyze chemical transformations. Group 4 diisopropoxide and Zn complexes were evaluated for the homopolymerization of lactide, while titanium dichloride complexes were assessed for their ability to polymerize ethylene. Group 4 diisopropoxide catalysts were active towards the ring-opening polymerization (ROP) of lactide, in the absence of any solvent, at 130°C. All Zr complexes were more active than the corresponding titanium homologues. The rate constant of the bis(guanidine–phenolate) group 4 systems (1.17––3.21 × 10-4 s–1) were higher than those displayed with Ti(OiPr)4 (5.34 × 10-5 s–1), and Zr(OiPr)4·iPrOH (2.79 × 10-5 s–1 ). Polylactic acid produced by guanidine-based catalysts exhibited similar molecular weights and dispersity (Ð) values to those of the industrial standard catalyst Sn(Oct)2, as well as to the precursors Ti(OiPr)4 and Zr(OiPr)4. The guanidine–phenol ligand proved to be active for the ROP of lactide with a larger rate constant than the most active Zr-based catalysts. The bis(guanidine–phenolate) titanium dichloride complexes were successfully synthesized and evaluated for the homopolymerization of ethylene. The low activity (up to 1.1 kgPE mol–1h–1) of the titanium dichloride complexes was ascribed to the electron-donating ability of the guanidine fragment and the stereoarrangement imparted by the guanidine–phenolate ligand about the Ti center. Zn catalysts bearing guanidine– and amidine–phenolate ligands were synthesized and evaluated for the ROP of lactide under solvent-free conditions at 130°C. The catalyst with the best performance was only 3 times slower than the industrial standard Sn(Oct)2 when a 100 to 1 monomer to catalyst ratio was used. Most catalysts displayed heterotactic bias in the polylactic acid generated with molecular weights up to 4900 Da. Dispersity values (Ð) ranged from 1.2 to 2.3 and were considered acceptable. Proligands were tested for the ROP of lactide, proving that their participation in the polymerization process cannot be ruled out. This new class of ligands and the corresponding complexes offer great potential and have a great deal of room for improvement.Author owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.ChemistryInorganic chemistryPolymer chemistryElectronic Thesis or Dissertation2025-11-11Polylactic acidPolymerization of lactideCatalystsGroup 4 complexesZinc complexesGuanidine-based ligandsAmidine-based ligandsLigand design