Organometallic chemistry of metalloporphyrins and controlled radical polymerization in aqueous media

Rhodium(II) porphyrins react with dihydrogen, carbon monoxide and olefins to form a diverse range of complexes including metal hydrides, metalloformyl and organometallic species in hydrocarbon solvents. One of the central objectives of this project has been to explore the scope of organometallic transformations mediated by rhodium porphyrins in water. The first part of this thesis focuses on the reactions of tetra (4-sulfonatophenyi)porphyrinato rhodium(III), Na ₃[(TSPP)Rh(D₂O)₂], in water with dihydrogen, carbon monoxide and olefins to form hydride, formyl and β-hydroxy alkyl derivatives. Aqueous reactions of [(TSPP)RhII]−4 occur through a rhodium rhodium bonded dimer which reacts with alkenes to form alkyl bridged complexes. Results in water are compared to systems previously studied in organic solvents. These reactions in water are highly pH dependent, a characteristic which facilitates tuning the equilibrium into a regime where equilibrium constants can be measured using 1H NMR techniques.; The second half of this work describes low spin cobalt(II) complexes with macrocyclic and non-macrocyclic ligand systems in both organic and aqueous media and the interactions between these metal centered radicals and organic radicals. Cobalt(II) porphyrin systems have previously been utilized in the controlled radical polymerization of acrylates with both living radical and chain transfer behavior. Kinetic studies presented herein substantiate the primary mechanistic features proposed for the porphyrin metalloradical controlled effective living polymerization and are used to determine the activation parameters for this process. A water soluble cobalt porphyrin, tetra (4-sulfonatophenyl)porphyrinato cobalt(II), [(TSPP)Co]−4, is synthesized and applied to aqueous phase radical polymerization. [(TSPP)Co]−4 was demonstrated to control an effective chain transfer catalytic process in the aqueous polymerization of methacrylic acid. Low spin nonmacrocyclic cobalt(II) complexes designed for application to chain transfer reactions in hydrocarbon solvent, demonstrated a dichotomy between the low ligand steric demand requisite for chain transfer reactions and the needed ligand substitution required to solublize the cobalt complex in organic solvents.