Disputas - Master of Science Marc Ferry Obst

Title of the thesis:

"Homogeneous Metal-Mediated Carboxylation with Carbon Dioxide"

Popular scientific abstract:

CO₂ is a non-toxic, abundant and readily available gas, which has the potential to become an important carbon source in chemical synthesis. The clear advantage of CO₂ is its sustainability, in contrast to typical carbon sources such as oil, coal, or natural gas, which are in the process of depletion. However, the use of CO₂ also poses a big challenge as it features a high thermodynamic and kinetic stability. Therefore, the aim of this thesis is to help in overcoming the chemical inertness of CO₂ by computational investigation of CO₂-converting catalysts. Catalysts are generally an important tool in chemical synthesis, and their ability to decrease activation energies could help enabling a wider use of CO₂ as a carbon source. In this work we concentrated our enquiry on homogeneous catalysts, as they feature defined reactive species and large reactive surfaces. For the metal center, we concentrated on base transition metals, such as Cu or Ni, which are less understood and considerably less expensive than the more commonly used heavy transition metals. We were especially interested in C-C bond forming reactions with CO₂ as they constitute new reaction routes, giving access to chemicals such as carbonates or pharmaceuticals. By using computational chemistry and cooperating with experimental chemists, we where able to gain insight into CsF-, Cu- and Ni-mediated carboxylation reactions. The results of these investigations yielded several interesting findings: First, a reaction mechanism for Cs-mediated carboxylation of organoboranes was identified which was able to explain the observed substrate preference and predicts an organocaesium intermediate. Second, the reaction mechanism for Cu- IPr-catalyzed carboxylation of organoboranes was investigated showing the formation of an organocopper intermediate before the insertion of CO₂ and yielding different behaviours for the Cu-CO₂ interaction, depending on the electronic nature of the coordinating carbon atom. The calculation of IR spectra for Phen-Ni(I)-alkyl species helped identifying their thermally unstable carboxylation products and the calculation of the CO₂ insertion TSs support the conclusion of strong Ni-CO₂ interactions.

The thesis is published in Munin and available at : https://hdl.handle.net/10037/18958

Supervisors:

• Associate Professor Kathrin Helen Hopmann, Department of Chemistry, Faculty of Science and Technology, UiT (main supervisor)
• Professor Luca Frediani, Department of Chemistry, Faculty of Science and Technology, UiT
• Associate Professor Annette Bayer, Department of Chemistry, Faculty of Science and Technology, UiT

Evaluation committee:

• Professor Stuart Macgregor, Institute of Chemical Sciences, Heriot-Watt University, UK (1st opponent)
• Principal Investigator Dr. Amalia Poblador-Bahamonde, University of Geneva, Switzerland (2nd opponent)
• Postdoc Dr. Bjarte Aarmo Lund, Department of Chemistry, Faculty of Science and Technology, UiT (internal member and leader of the committee)

Reserve member : Dr. Ainara Nova, Department of Chemistry, The faculty of Mathematics and Natural Sciences, University of Oslo.

Leader of the public defense:

The leader of the public defense is Professor Camilla Brekke,Vice-Dean Research, Faculty of Science and Technology, UiT.

If you have any questions for the candidate during the public defence, please send an e-mail to the leader of the public defence. They will announce the questions during the defence.

Trial lecture:

The trial lecture is held on Friday, 4th September at 10:15 AM in the same auditorium.

Title of the trial lecture:

«The interplay between DFT and experimental studies on Grubbs- Metathesis catalysis - from simple to advanced models»

Streaming:

The defense and trial lecture will be streamed via Mediasite: https://mediasite.uit.no/Mediasite/Catalog/Full/64a9a4ecd00c4677aaf27b84ffd580fc21

Audience:

UiT follows the national guidelines regarding infection control. A maximum of 20 people are allowed in the auditorium during the defence, as long as everybody keeps a distance of 1 meter at all times.