Development and exploration of Schiff base ruthenium carbene catalysts for olefin metathesis

The PhD contains to parts. In the first part, an extensive overview is presented on the history of metathesis catalysts, the current ideas in organometallic thinking and the theoretical accounts on Ru-metathesis catalysts. The second part deals with the synthesis and activity of Schiff base substituted second generation Grubbs catalysts, bimetallic Schiff base substituted Grubbs catalysts, the development of new NHCs (N-Heterocyclic Carbene) for the 2nd generation Grubbs catalysts and a detailed investigation of secondary metathesis events. The Schiff base substituted second generation Grubbs catalysts were synthesized, proving a previous synthesis was incorrect. The new synthesis was confirmed with NMR and crystal structure analysis. A series of ten of these catalysts was synthesized and their activity was screened for several metathesis reactions. The main advantages lie in the stability of the catalysts which is expressed in challenging reactions, such as the RCM (Ring Closing Metathesis) in methanol and the RCM of disubstituted olefines. We also attempted to synthesize the bimetallic Schiff base substituted Grubbs catalysts, though we showed that here also the previous account of these catalysts was incorrect. In fact, the catalysts can not be synthesized because a disproportionation destroys the complex. Using the extensive analysis made in the theoretical piece on organometallic chemistry and theoretical accounts on Ru-metathesis catalysts, a strategy was proposed for new NHC ligands. We focused on the installation of a pi-acceptor function in the NHC, which is also interesting as a fundamental research in organometallic chemistry. We achieved in preparing an (amino)(amido)NHC which showed this characteristic and when this ligand was substituted on the Grubbs catalyst, the resulting catalysts showed faster initiation than the classical second generation catalysts for the ROMP (Ring Closing Metathesis Polymerization) of COD (Cyclooctadiene). Also the secondary metathesis was intensively investigated. We showed that the second generation Grubbs catalysts were able to lead any form of the COD-polyCOD-CDT (Cyclododecatriene) mixture to equilibrium. The first generation catalysts were unable to perform transformations concerning COD. It was also shown that the catalyst leaves a fingerprint on all polymers in the beginning of ROMP, which disappears after time due to secondary metathesis.

Author dc:creator

• Allaert, B

Contributors dc:contributor

• Verpoort, F

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

und

Identifier

https://biblio.ugent.be/publication/472499
http://doi.org/1854/8896
https://biblio.ugent.be/publication/472499/file/1880743

OAI identifier oai:identifier

oai:archive.ugent.be:472499