C-H on the Oxo Ferryl Wheel: Comparison of Pyridine and Imidazole-Substituted Ligands for C-H Activation and Functionalization

<p>The selective and efficient transformation of hydrocarbon feedstocks is of high value for industry and research. While Shilov-type organometallic methods have facilitated this goal, systems designed after nature’s use of cheap and abundant iron-based enzymes are desired for wider-scale applications. This work establishes hydrocarbon oxidation efficiency of synthetic pyridine-based ligands (BPMEN, BPMPN) compared to commercially available TPA with <em>in situ</em> generated catalysts. Literature studies of traditionally synthesized BPMEN systems and initial <em>in situ </em>studies offered evidence for enhanced reactivity (TON) as compared to TPA. Expansion to a propyl backbone to produce BPMPN tested the increased chelate ring size’s impact on reactivity as compared to BPMEN. Optimized catalysis yielded higher TON efficiency with BPMEN as well as greater selectivity compared to TPA across all substrates and conditions. Utilization of the BPMPN architecture not only offered lower TON as compared to the BPMEN precursor, but resulted in excessively low product yields below that of TPA, often near or below the limit of quantification. We next turned to addressing the lack of imidazole-substituted models through ligands BItCHEN and ^nBuBIMEN. Translating the previously established BItCHEN structure to our simple and modular synthetic approach ultimately proved unsuccessful. Therefore, we focused on ^nBuBIMEN, established by our collaborator. Preliminary investigations indicated that while this ligand was less effective for oxidation, epoxidation capability was near or above that of BPMEN. Interestingly, ^nBuBIMEN also showed evidence of a more stable oxo-species intermediate, leading to computational assessment of oxo stability across these scaffolds.</p>

Name thesis:degree_name

Master of Science in Natural Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemistry and Biochemistry

Year dc:date.available

2022

Author dc:creator

• Milem, Elizabeth

Contributors dc:contributor

• John Brannon Gary

• in situ
• non-heme oxo
• catalysis
• biomimetic
• C-H functionalization
• C-H activation
• Inorganic Chemistry
• Organic Chemistry

Repository record dc:identifier

https://scholarworks.sfasu.edu/etds/437

OAI identifier oai:identifier

oai:scholarworks.sfasu.edu:etds-1481