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Abstract

This thesis describes the studies of reactions of CO2 with olefin polymerization catalysts and analogous metal alkyl complexes. These metal alkyl complexes differ by the number of alkyl groups, charges and coordination sites and thus provide insights to how these factors affect the carboxylation of olefin polymerization catalysts. Chapter One introduces the scope and mechanisms of the reactions of metal alkyl complexes with CO2. These reactions can occur by a spectrum of mechanisms. Structure/reactivity relationships and mechanistic studies of these reactions are discussed. Chapter Two describes structure/reactivity and DFT studies of the carboxylation reactions of Cp2ZrMe(ClC6D5)+ and (PO-iPr)PdMe (PO-iPr– = 2-PiPr2-4-Me-C6H3SO3–) complexes, and their corresponding dimethyl complexes Cp2ZrMe2 and (PO-iPr)PdMe2-. CO2 reacts with Cp2ZrMe(C6D5Cl)+ more than 104 faster than with Cp2ZrMe2, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO2, and the electrophilicity of the Zr center controls the reactivity. In contrast, CO2 reacts readily with anionic [(PO-iPr)PdMe2]− to yield [(PO-iPr)PdMe(OAc)]− but not with neutral (PO-iPr)PdMe(L) species. Carboxylation of [(PO-iPr)PdMe2]− occurs by direct SE2 attack of CO2 at the Pd–Metrans-to-P group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the SE2 process is accelerated by a Li+- - -OCO interaction when Li+ is present. Chapter Three describes mechanistic studies of reactions of CO2 with (PDI)FeMe, (PDI)Fe(Me)PMe3 and [(PDI)FeMe][BPh4]. Solvent effects and kinetic studies provide evidence that these reactions occur by an insertion mechanism involving CO2 pre-coordination to the Fe center regardless of charge state. CO2 reacts with neutral (PDI)FeMe 5-fold faster than with cationic [(PDI)FeMe][BPh4], suggesting that the nucleophilicity of Fe–Me group controls the reactivity.

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