Reduction of CO2 and CO Mediated by Transition Metal Complexes Public Deposited

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  • March 20, 2019
Creator
  • Massey, Marsha
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • The direct correlation of increasing worldwide energy demand with increasing CO2 emissions presents a compelling need to devise a method of alternative energy production that will meet demand but limit further CO2 release into the atmosphere. Catalytic reduction of carbon dioxide to produce a renewable fuel source could be a viable solution, and developing approaches for the conversion of CO2 to fuel is a current area of intense research activity. The work presented here focuses on evaluation of molecular complexes capable of reducing CO2. Chapter 2 considers a ligand-based hydride transfer approach for carbon dioxide reduction to formate using two new manganese cyclohexadienyl complexes of formulation Mn(η5-C6Me6H)(CO)L2 with L2 as a bidentate phosphine ligand. The reductive capabilities of the manganese complexes are demonstrated in reactions with carbon disulfide to form dithioformate at room temperature. Chapter 3 explores the reactivity of the CO reduction intermediate hydroxymethyl ligand in [Ru(bpy’)2(CO)(CH2OH)][PF6] (bpy’ = 5,5’-dimethylbipyridine) that has been proposed to be a precursor to MeOH. Reaction with acids and other electrophiles occur at oxygen rather than carbon of the hydroxymethyl ligand, to produce a series Lewis base stabilized carbene complexes (ylide complexes). Of particular interest are the labile nitrile ylide complexes that are shown to be precursors to the C-C coupled product, ethylene. This system highlights the potential to achieve C2 products via CO reduction. Finally, Chapter 4 presents synthetic routes to new ruthenium carbonyl complexes incorporating the bidentate carbene-pyridine ligand, 3-methyl-1-picolylbenzimidazol-2-ylidene (Mebim-pic) to compliment prior studies of 3-methyl-1-pyridylbenzimidazol-2-ylidene (Mebim-py). The methylene spacer between the pyridine and carbene ligands in the Mebim-pic system gives rise to a larger bite angle (87.2°) in comparison to Mebim-py (77.9°), which will change the steric environment at the catalytic site. Synthetic routes to carbonyl complexes [Ru(Mebim-pic)(tpy)(CO)]2+ (where tpy is 2,2’:3’3”-terpyridine) and [Ru(Mebim-pic)(bpy’)(CO)2]2+ are reported. Carbonyl complexes are intermediates in the catalytic cycle for reductive disproportionation of CO2 as well as the entry point to further reduction of the coordinated CO ligand.
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  • In Copyright
Advisor
  • Schauer, Cynthia
  • Gagne, Michel
  • Brookhart, Maurice
  • Miller, Alexander
  • Dempsey, Jillian
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2016
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