Exploration of Metal-Carbonyl Complexes for Decarbonylation Reactions

In recent years, transition metal-mediated decarbonylation reactions have emerged as an alternative to conventional cross-coupling methods due to the advantages associated with the use of carbonyl-containing functionalities as coupling electrophiles instead of organohalides found in traditional cross-coupling reactions. This, coupled with the ubiquity of carbonyl-containing compounds in pharmaceuticals and non-biodegradable chemicals, has led to the interest in developing efficient systems for transition metal-catalyzed decarbonylation. However, these reactions are commonly limited to stoichiometric amounts of metal reagents due to the strong metal-carbonyl bond formed during transition metal-mediated decarbonylation. With the goal of gaining a better mechanistic understanding of CO dissociation in relation to decarbonylation reactions, this thesis demonstrates the synthesis, isolation, and characterization of both iron and nickel complexes and their respective decarbonylation and carbonylation reactivities. The first chapter outlines traditional methods for the synthesis and decarbonylation of transition metal carbonyl complexes and discusses the application of transition metal-carbonyl complexes towards the decarbonylation and diversification of organic compounds. The second chapter details the synthesis, isolation, and characterization of a cationic, facially capped iron(II) carbonyl complex. A series of ligand substitution experiments indicate that the scorpionate ligand promotes CO ligand exchange from a low-valent iron carbonyl complex. The third chapter details the synthesis, isolation and characterization of a N-phenylbenzamide nickel(II) complex; a complex which can undergo reversible carbonylation. As a continuous effort in deepening mechanistic investigations, this metal complex has also demonstrated success in enabling nickel-mediated decarbonylative coupling of boronic acids, indicating the importance as a possible intermediate. The fourth chapter details our efforts towards understanding the affect electronic influences have on regioselective nickel-mediated decarbonylation. Through the synthesis, isolation, characterization, and study of the fundamental CO exchange reactivity in relevant transition metal-carbonyl complexes we demonstrated that CO ligands can be readily exchanged under our conditions, providing insight into the further development of metal-mediated decarbonylation reactions