N-heterocyclic carbene ligands designed for improved stability and efficiency of ruthenium-based olefin metathesis catalysts / Pawel Krzesinski  

Public ISBD Titre : N-heterocyclic carbene ligands designed for improved stability and efficiency of ruthenium-based olefin metathesis catalysts Type de document : texte imprimé Auteurs : Pawel Krzesinski, Auteur ; Vincent Cesar, Directeur de thèse ; Karol Grela, Directeur de thèse Langues : Anglais (eng) Tags : ORGANOMETALLIC COMPLEXES  N-HETEROCYCLIC CARBENES  HOMOGENEOUS CATALYSIS  RUTHENIUM  COORDINATION CHEMISTRY  Z SELECTIVITY Résumé : "No doubt catalysis is one of the most relevant tools used in the chemical industry, allowing to obtain a myriad of sometimes otherwise inaccessible molecules. Catalyst's auxiliary ligands play a significant role in defining the activity, selectivity and stability of the resulting catalysts. In this respect, N-heterocyclic carbene (NHC) ligands have shown a broad utility as spectator ligands that can stabilize catalytic intermediates. The most important impact of NHCs is arguably in the field of olefin metathesis (OM), a reaction that has already become a device of prominent importance in organic synthesis. The work described here aimed at NHC ligand design to achieve more stable, durable and thus more efficient OM catalysts. Two strategies were investigated to enhance the stability of corresponding NHC OM catalysts. The thesis is divided into six chapters. The first chapter of the thesis describes relevant state-of-the-art. In the second chapter, a strategy for a robust Z-selective OM catalyst was investigated, followed by chapter three reporting catalysts designed for an efficient tetrasubstituted carbon-carbon double bond formation. The last part of the work describes in chapter four a potential application of the obtained catalytic systems. The thesis concludes with an experimental section and references in chapters five and six respectively. Within the first strategy for a more efficient catalyst, attempts to obtain a robust Z-selective catalyst bearing a chelating LX-type NHC ligand were explored by altering the X-type carbon-based ligand. The research objectives were diversified into two axes, where a synthesis of OM catalysts bearing bidentate NHC ligands comprising either a barbituric heterocycle (axis A) or N-heterocyclic olefin (NHO) moiety (axis B) were attempted. Several ruthenium(II) complexes bearing the targeted NHC-barbiturate ligand were successfully synthesized. However, the corresponding OM catalyst could not be obtained and a mechanism was proposed to explain the observed reactivity. In the next part, the synthesis of an NHC-NHO OM catalyst was attempted. However, the formation of the corresponding ruthenium-NHC complex was precluded due to an unexpected ring opening of the formed imidazolinylidene heterocycle. The reactivity of the novel class NHC-NHO ligand was explored in the coordination chemistry of rhodium(I) and palladium(II) metal centers, ultimately leading to the synthesis of the first NHC-NHO complex based on a palladium platform. The third chapter is based on a second strategy for a more efficient catalyst, presenting advancements in the formation of tetrasubstituted carbon-carbon double bonds using OM. Considering that the anticipated, deleterious catalyst deactivation pathway requires the rotation of the N-aryl arm of the NHC ligand, a second decker of aromatic groups in benzimidazolylidene-based N-phenyl NHC ligands was introduced. This led to robust and highly efficient ruthenium OM catalysts in challenging metathesis reactions of tri- and tetra-substituted olefins. The beneficial effect of these upper aromatic ''wings'' on the stability and activity of ruthenium complexes is rationalized through the experimental determination of the stereoelectronic properties of the NHC ligands, complemented by DFT calculations on the nature of the through-space interactions between the aromatics and on the decomposition pathway of precatalysts. At last, the obtained catalytic systems were tested in the synthesis of bio-based polyesters and polyamides. To demonstrate the applicability of this study, a technical grade methyl oleate was used for the self-cross metathesis step. Such material derives from broadly available sunflower or rapeseed oil and contains a substantial amount (20 wt%) of methyl linoleate. The obtained dimethyl octadec-9-enedioate was used in a subsequent polycondensation with a co-monomer (diol or diamine), which resulted in the formation of polymeric materials." Document : Thèse de Doctorat Etablissement_delivrance : Université Toulouse 3 Date_soutenance : 12/02/2024 Ecole_doctorale : Sciences de la matière (SdM) (Toulouse) Domaine : Chimie Organométallique et de Coordination En ligne : https://theses.fr/2024TLSES006 N-heterocyclic carbene ligands designed for improved stability and efficiency of ruthenium-based olefin metathesis catalysts [texte imprimé] / Pawel Krzesinski, Auteur ; Vincent Cesar, Directeur de thèse ; Karol Grela, Directeur de thèse . - [s.d.]. Langues : Anglais (eng) Tags : ORGANOMETALLIC COMPLEXES  N-HETEROCYCLIC CARBENES  HOMOGENEOUS CATALYSIS  RUTHENIUM  COORDINATION CHEMISTRY  Z SELECTIVITY Résumé : "No doubt catalysis is one of the most relevant tools used in the chemical industry, allowing to obtain a myriad of sometimes otherwise inaccessible molecules. Catalyst's auxiliary ligands play a significant role in defining the activity, selectivity and stability of the resulting catalysts. In this respect, N-heterocyclic carbene (NHC) ligands have shown a broad utility as spectator ligands that can stabilize catalytic intermediates. The most important impact of NHCs is arguably in the field of olefin metathesis (OM), a reaction that has already become a device of prominent importance in organic synthesis. The work described here aimed at NHC ligand design to achieve more stable, durable and thus more efficient OM catalysts. Two strategies were investigated to enhance the stability of corresponding NHC OM catalysts. The thesis is divided into six chapters. The first chapter of the thesis describes relevant state-of-the-art. In the second chapter, a strategy for a robust Z-selective OM catalyst was investigated, followed by chapter three reporting catalysts designed for an efficient tetrasubstituted carbon-carbon double bond formation. The last part of the work describes in chapter four a potential application of the obtained catalytic systems. The thesis concludes with an experimental section and references in chapters five and six respectively. Within the first strategy for a more efficient catalyst, attempts to obtain a robust Z-selective catalyst bearing a chelating LX-type NHC ligand were explored by altering the X-type carbon-based ligand. The research objectives were diversified into two axes, where a synthesis of OM catalysts bearing bidentate NHC ligands comprising either a barbituric heterocycle (axis A) or N-heterocyclic olefin (NHO) moiety (axis B) were attempted. Several ruthenium(II) complexes bearing the targeted NHC-barbiturate ligand were successfully synthesized. However, the corresponding OM catalyst could not be obtained and a mechanism was proposed to explain the observed reactivity. In the next part, the synthesis of an NHC-NHO OM catalyst was attempted. However, the formation of the corresponding ruthenium-NHC complex was precluded due to an unexpected ring opening of the formed imidazolinylidene heterocycle. The reactivity of the novel class NHC-NHO ligand was explored in the coordination chemistry of rhodium(I) and palladium(II) metal centers, ultimately leading to the synthesis of the first NHC-NHO complex based on a palladium platform. The third chapter is based on a second strategy for a more efficient catalyst, presenting advancements in the formation of tetrasubstituted carbon-carbon double bonds using OM. Considering that the anticipated, deleterious catalyst deactivation pathway requires the rotation of the N-aryl arm of the NHC ligand, a second decker of aromatic groups in benzimidazolylidene-based N-phenyl NHC ligands was introduced. This led to robust and highly efficient ruthenium OM catalysts in challenging metathesis reactions of tri- and tetra-substituted olefins. The beneficial effect of these upper aromatic ''wings'' on the stability and activity of ruthenium complexes is rationalized through the experimental determination of the stereoelectronic properties of the NHC ligands, complemented by DFT calculations on the nature of the through-space interactions between the aromatics and on the decomposition pathway of precatalysts. At last, the obtained catalytic systems were tested in the synthesis of bio-based polyesters and polyamides. To demonstrate the applicability of this study, a technical grade methyl oleate was used for the self-cross metathesis step. Such material derives from broadly available sunflower or rapeseed oil and contains a substantial amount (20 wt%) of methyl linoleate. The obtained dimethyl octadec-9-enedioate was used in a subsequent polycondensation with a co-monomer (diol or diamine), which resulted in the formation of polymeric materials." Document : Thèse de Doctorat Etablissement_delivrance : Université Toulouse 3 Date_soutenance : 12/02/2024 Ecole_doctorale : Sciences de la matière (SdM) (Toulouse) Domaine : Chimie Organométallique et de Coordination En ligne : https://theses.fr/2024TLSES006

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