Year of Award
2026
Document Type
Dissertation
Degree Type
Doctor of Philosophy (PhD)
Degree Name
Chemistry
Other Degree Name/Area of Focus
Bioinorganic Chemistry
Department or School/College
Department of Chemistry and Biochemistry
Committee Chair
Orion B. Berryman
Commitee Members
Dong Wang, Bruce E. Bowler, Kent D. Sugden, J. Stephen Lodmell
Keywords
Aliphatic C-H Bond Activation, Catalyst Design, Functionalization, Metal Oxo, Non-Oxo Species, Predictive System
Abstract
Activation of inert carbon-hydrogen (C-H) bonds remains a challenge in synthetic chemistry. High-valent metal-oxo species serve as nature’s oxidants, but their transient nature limits systematic study and subsequent tuning of their reactivity. This dissertation establishes a predictive blueprint for C-H activation using a tunable, redox-active Cobalt(IV) pincer system (LCoIVX2), isolating the topological and electronic variables governing oxidation mechanisms. We discovered that anion topology dictates kinetic distribution. For example, strong axial σ-donors induce a ground-state orbital inversion (d(z2) → d(yz)) that relaxes spatial reactivity demands, and, for some ancillary ligands, a conduit effect drives increased HAT rates by delocalizing the oxidative hole.
Late transition metals reside beyond the theoretical “oxo wall,” precluding stable terminal metal-oxo complexes. Utilizing a non-oxo cobalt system circumvents this structural limitation. Applying our calibrated predictive model to this surrogate system successfully extrapolates the effective basicity and intrinsic reactivity of the elusive M=O moiety. Fortuitously, thermodynamic profiling revealed the reaction solvent acts as a non-innocent participant in high-valent cobalt chemistry, where outer-sphere reorganization penalties impose energetic impedance on reactivity. This slowed reaction speed allowed for the successful kinetic capture of the M=O reaction rate, providing an opportunity to utilize the prediction system produced herein to uncover the thermodynamic properties previously hidden by conventional methods. Further testing of thermodynamic limits with basic anions exposes catalyst turnover capacity and ligand backbone vulnerabilities.
Finally, this work presents the mechanistic picture of high-valent cobalt-mediated C-H bond activation. The decoupling of geometric reorganization from thermodynamic driving force yields a multi-tiered Hierarchy of Orbital Tuning Parameters to guide rational catalyst design.
Recommended Citation
Kayne, Michael Anthony, "TUNING THE ELECTRONIC STRUCTURE AND REACTIVITY OF MONONUCLEAR HIGH-VALENT COBALT(IV) COMPLEXES FOR C-H BOND ACTIVATION" (2026). Graduate Student Theses, Dissertations, & Professional Papers. 12614.
https://scholarworks.umt.edu/etd/12614
© Copyright 2026 Michael Anthony Kayne