Non-noble metal catalysis for Cross-coupling reactions: Computational insights
Catalysis plays a pivotal role in our society since we are critically dependent on plastic materials and pharmaceutical products of which many steps of their industrial production are led by catalyzed processes.
Accordingly, the development of a new catalytic systems based on transition metals is very active.
However, catalysts are, nowadays, mainly made by organometallic complexes based on rare and precious noble metals such as Pd, Pt, Ir.
These types of catalysts made out of noble metals are very efficient, however, they carry with their performances the drawback of being highly toxic, scarce, and expensive.
This aspect is forcing the catalysis field to move on to the development of catalysts based on non-noble metals such as Fe, Ni, and Co.
The aim of this thesis and the related results are contained in these statements.
By the use of computation, we tried to get some advances in the understanding of some reaction mechanisms of non-noble metal-catalyzed processes.
We used density functional theory (DFT) to study some challenging chemical reactivity and complicated reaction mechanisms.
Specifically, we focused on three processes: two cross-coupling reactions catalyzed by either iron or nickel complexes and an amidation reaction catalyzed by Ni complexes. Generally, we were able to provide some insights into the reaction mechanisms involved during these reactions. We could also suggest and rule out some intermediates and reaction steps of which it is difficult to account for experimentally.
In summary, the first project is about an iron-catalyzed reductive coupling of which we were not able to draw a definitive reaction mechanism, however, we provided some insights, such as ruling out the presence of a discrete Fe(I) reduced species, and suggesting that a halogen transfer reaction carried out by solid zinc might be important.
In the second project, we collaborate with the group of Prof. Hu in EPFL providing a suitable reaction mechanism for the amidation reaction of esters catalyzed by Ni complexes. In this project with the use of computation, we could suggest a NiZn-heterodimer as the potential nucleophile of the reaction. The third and last project is about the Negishi arylation of propargyl bromides catalyzed by Ni complexes.
In this project, we were able to rule out the presence of a Ni(I) species and also able to suggest that a previously unidentified halogen transfer step plays an important role in catalyst pre-activation.
In conclusion, with the use of computation, we were able to tackle some challenges in the reaction mechanisms of the processes under study.