Part I. Oxorhenium Catalyst Design for Oxygen Atom Transfer Methodologies
Abstract
As our global fossil fuel deposits diminish, population continues to increase on a global scale and more countries become industrialized, the standard of living has shifted and the need for alternative fuel and chemical feedstocks on a massive scale is a task that must be considered with the utmost gravity. Catalytic conversion of biomass-derived oxygenates (including cellulosic carbohydrates and lignin) provides an opportunity to offset this deficit of value-added chemicals and fuels. The development of efficient and selective catalysts for oxygen atom transfer (OAT) methodologies is essential in order to facilitate upgrading biomass-derived oxygenates to furfural and hydrocarbon fuel chemicals; the first part of this thesis details developments in this field. A heterogeneous, carbonaceous, solid-acid catalyst containing both and Brønsted and Lewis acidity was studied in the context of carbohydrate conversion to 5-(hydroxymethyl)furfural (HMF) and furfural (Ff), one of these relevant platform chemical reaction pathways. Here, reactions were performed with carbohydrates relevant to biomass conversion using a microwave reactor system for significant efficiency. It was found, that from a variety of mono- and disaccharides, that furfural products (HMF or Ff, depending upon the carbohydrate source) could be obtained in good to excellent yield with this dual acidic catalyst. Due to the considerable propensity for oxorhenium compounds to catalyze OAT reactions, the synthesis and characterization of various homogenous oxorhenium pincer complexes was investigated. The addition of a pincer ligand provides an opportunity to enhance the reactivity of the overall complex through potential metal-ligand cooperativity. We found a series of peculiar dioxocarbonyl complexes that resulted with reaction of carbon monoxide, a major C1 source, often derived from CO2, with great relevance in value-added chemical development methodologies. These complexes provide precedent for an isolable coordination complex possessing conflicting ligand environments, featuring the π-donor oxo ligands and π-acceptor carbonyl ligand. Expanding upon the investigation of the reactivity of these oxorhenium pincer complexes, the use of the oxo ligand as an “auxiliary coordination site” for electrophilic species was pursued. A catalytic cycle for the hydrosilylation of CO2, a potent greenhouse gas and abundant C1 source, was achieved with excellent selectivity and excellent to good yields of the corresponding formate, formal and methanol oxidation state products. Selectivity of the CO2 reduction product formed can be arbitrated by the organosilane employed, thus allowing for a one pot conversion process from CO2 to silyl methanol. The second part of this thesis details explorations in bioinspired adhesive polymer design. Mussels, barnacles and oysters have mastered the art of underwater adhesion, an essential component of biomedical adhesive design. We take inspiration from these marine creatures in designing novel polymeric systems that can confront the challenges associated with modern adhesives, specifically toughening. Results described herein center around poly{[dopamine methacrylamide]-co-[acrylic acid]}, a polymeric mimic of mussel adhesive proteins. The acrylic acid moieties provide “sacrificial bonds” that provide ductility and strength, a general strategy for toughening an adhesive material. A variety of additives featuring two functional groups were screened and it was found that alcohol and polyol compounds provide optimal results in the context of promoting toughening of the adhesive bond
Degree
Ph.D.
Advisors
Wilker, Purdue University.
Subject Area
Inorganic chemistry
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