Investigations of homogeneous ruthenium and cobalt complexes for electrocatalytic transformations
Abstract/Contents
- Abstract
- Transition metal hydrides are key intermediates implicated in a wide range of chemical and electrochemical transformations. Herein, select examples of molecular transition metal hydride complexes and their applications in critical hydrogen transfer reactions, specifically transfer hydrogenation, electrocatalytic alcohol oxidation, and electrocatalytic hydrogen evolution, are presented. An octahedral Ru-hydride complex reacts rapidly and irreversibly with CO2 under ambient conditions to yield the Ru-formate. The analogous insertion of various ketones yields an equilibrium mixture of the hydride and alkoxide complexes, for which the equilibrium constants are measured by 1H NMR. Density functional theory is used to compare the mechanism of acetone and CO2 insertion. Investigations on the kinetic profile of transfer hydrogenation with the Ru-hydride complex reveal some key aspects of the mechanism. The Ru-hydride undergoes an irreversible oxidation at low potential by cyclic voltammetry. In the presence of alcohol and alkoxide base, large current enhancement is observed at this potential, consistent with electrocatalytic alcohol oxidation. The synthesis and characterization of a family of dicationic Co(III) complexes with bidentate nitrogen ligands are presented. Upon addition of protonated N, N-dimethylformamide buffer, electrocatalytic hydrogen evolution is observed at onset potentials near -1.1 V. Further studies demonstrate that these complexes decompose under acidic reducing conditions to form an active species at the electrode surface. A Co(III)-azopyridine complex exhibits a reversible 2e- reduction at very mild potentials. Chemical reduction with cobaltocene yields a neutral complex as an air stable, diamagnetic solid. Spectroscopic and crystallographic studies illuminate key structural and electronic changes that occur upon reduction, indicating that the neutral complex is best described as a highly delocalized system. Protonation of the neutral species yields a monocationic hydrazino complex. All three cleavage modes (i.e. proton, hydride, and hydrogen atom) for this ligand N-H bond are demonstrated. Studies on the stoichiometric reactivity of this complex with the triphenylcarbenium cation and TEMPO radical are explored.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Waldie, Kate M |
|---|---|
| Associated with | Stanford University, Department of Chemistry. |
| Primary advisor | Waymouth, Robert M |
| Thesis advisor | Waymouth, Robert M |
| Thesis advisor | Chidsey, Christopher E. D. (Christopher Elisha Dunn) |
| Thesis advisor | Xia, Yan |
| Advisor | Chidsey, Christopher E. D. (Christopher Elisha Dunn) |
| Advisor | Xia, Yan |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Kate M. Waldie. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Kate MacKenzie Waldie
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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