Vanadium Alkylidene Complexes for Olefin Metathesis

Authors

Gabriela Tejeda, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Konstantin Bukhryakov

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Raphael Raptis

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Kevin O'Shea

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Daniela Radu

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Kathleen Rein

Fifth Advisor's Committee Title

Committee member

Keywords

Organometallic Chemistry, Vanadium, Alkylidene, Olefin Metathesis, Catalysis

Date of Defense

3-8-2023

Abstract

Olefin metathesis (OM) is a powerful method used for the formation of C-C bonds. It can be categorized into three major groups: Ring Opening Metathesis (ROM), Ring Closing Metathesis (RCM), and Cross Metathesis (CM). OM catalysts are used in the industry and the synthesis of pharmaceuticals and natural products. Well-known metathesis catalysts employ second- and third-row transition metals such as Ru, Mo, and W. V, a first-row transition metal, can be used as a greener alternative since it is more abundant, less toxic, and more sustainable.

The Ring Opening Metathesis Polymerization (ROMP) of norbornene is the most studied reaction employing V alkylidenes. Our group synthesized a new class of V chloride alkylidenes with varying imido and neutral ligands which proved to be active towards RCM of substrates containing internal olefins. When exposed to terminal olefins, the catalyst’s instability towards ethylene, a side product of the reaction, prevented their high activity. According to Density Functional Theory (DFT) studies, b-hydride elimination is disfavored when the size and donating abilities of the neutral ligands increase therefore preventing catalyst degradation.

Our group then synthesized V N-heterocyclic carbene (NHC) alkylidenes active towards the RCM of terminal olefins. To date, the highest turnover number (TON) for RCM using V alkylidenes was obtained and the complexes can tolerate multiple organic functional groups. The formation of a less stable catalyst containing two phosphine groups as catalysis takes place prevents the higher productivity of this class of complexes. To temporarily address this problem, a phosphine scavenger was employed but a more permanent solution was necessary.

In the search for higher activity, V alkylidenes have been grafted onto Silica and Alumina supports. The heterogeneous catalysts have shown increased activity towards RCM of acyclic dienes compared to the corresponding molecular catalyst and their functional group tolerance is currently being studied. Some of the synthesized V complexes also demonstrate a unique preference for unproductive metathesis which can be used for isotope labeling studies, which is crucial in the pharmaceutical industry.

Identifier

FIDC011029

ORCID

https://orcid.org/0000-0001-7651-0726

Previously Published In

1. Belov, D. S.; Tejeda, G.; Bukhryakov, K. V., Olefin Metathesis by First-Row Transition Metals. ChemPlusChem 2021, 86 (6), 924-937

2. Belov DS, Tejeda G, Tsay C, Bukhryakov KV. Ring-Closing Olefin Metathesis Catalyzed by Well-Defined Vanadium Alkylidene Complexes. Chemistry – A European Journal. 2021;27(14):4578-82

3. Tejeda, G.; Belov, D. S.; Fenoll, D. A.; Rue, K. L.; Tsay, C.; Solans-Monfort, X.; Bukhryakov, K. V., Vanadium Imido NHC Complexes for Ring-Closing Olefin Metathesis Reactions. Organometallics 2022, 41 (4), 361-365

Recommended Citation

Tejeda, Gabriela, "Vanadium Alkylidene Complexes for Olefin Metathesis" (2023). FIU Electronic Theses and Dissertations. 5294.
https://digitalcommons.fiu.edu/etd/5294