Synthesis of iron amino-bis(phenolate) complexes and their application in ring-opening copolymerizations

Abstract

Three iron amino-bis(phenolate) complexes featuring differing pendant donor groups were synthesized in this work. The structures include pyridyl, morpholinyl and amine groups, respectively, and were characterized by various techniques including MALDI-TOF MS, UV-Vis spectroscopy and single crystal X-ray diffraction. These complexes were further explored for the potential synthesis of cationic iron amino-bis(phenolate) complexes through halide abstraction with Lewis acids. The resulting reaction solutions were characterized by similar methods used to study the neutral complexes, including UV-Vis spectroscopy and MALDI-TOF MS. Metal-based amino-bis(phenolate) complexes, both neutral and cationic, have been previously used as catalysts in ring-opening polymerization (ROP) reactions. The use of earth abundant element-based catalysts, such as iron complexes, provides environmental and economic benefits to potential catalytic applications. Subsequently, the reactivity of the iron amino-bis(phenolate) complexes synthesized here, and their protioligands, was investigated for ring-opening copolymerization (ROCOP) reactions. This reaction screening studied the coupling of epoxides and anhydrides for polyester synthesis, as well as epoxides and CO₂ for selective poly- or cyclic- carbonate formation. The products obtained were characterized by ¹H NMR spectroscopy, GPC and MALDI-TOF MS, with CO₂ reactions monitored via in-situ FT-IR spectroscopy. The results of these studies will be presented and discussed throughout this thesis.