Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Catalytic ethylene oligomerization is a well understood industrially viable process. The large majority of scientific literature and patents concerning this process has been developed with the use of chromium catalysts. Commercial systems producing selective tri/tetramerization, non-selective oligomerization and polymerization are all based on this metal with the exception of a few systems based on other transition metals (Zr, Ti, Ni etc.). This versatility raises interesting questions about chromium’s unique behaviour. Essentially, selective or non-selective oligomerization and polymerization processes could be regarded as belonging to the same category of C-C bond forming reactions, though different mechanisms are involved. The first part of this thesis explores a variety of chromium complexes for ethylene oligomerization purposes. In order to gather further information about the unique behaviour of chromium, we have explored a variety of nitrogen and phosphorus containing ligands. We started with a simple bi-dentate anionic amidophosphine (NP) ligand and assessed the role of the ligand’s negative charge and number of donor atoms in determining the type of catalytic behaviour in relation to the metal oxidation state. This ligand proved capable of generating a series of chromium dimeric, tetrameric or polymeric and even heterobimetallic chromium-aluminate complexes in different valence states. This allowed us to isolate a “single component” self activating Cr(II) complex as well as a rare example of mixed valence Cr(I)/Cr(II) species. Additionally, each of these species acted as switchable catalyst depending on the type of co-catalyst

Catalytic ethylene oligomerization is a well understood industrially viable process. The large majority of scientific literature and patents concerning this process has been developed with the use of chromium catalysts. Commercial systems producing selective tri/tetramerization, non-selective oligomerization and polymerization are all based on this metal with the exception of a few systems based on other transition metals (Zr, Ti, Ni etc.). This versatility raises interesting questions about chromium’s unique behaviour. Essentially, selective or non-selective oligomerization and polymerization processes could be regarded as belonging to the same category of C-C bond forming reactions, though different mechanisms are involved. The first part of this thesis explores a variety of chromium complexes for ethylene oligomerization purposes. In order to gather further information about the unique behaviour of chromium, we have explored a variety of nitrogen and phosphorus containing ligands. We started with a simple bi-dentate anionic amidophosphine (NP) ligand and assessed the role of the ligand’s negative charge and number of donor atoms in determining the type of catalytic behaviour in relation to the metal oxidation state. This ligand proved capable of generating a series of chromium dimeric, tetrameric or polymeric and even heterobimetallic chromium-aluminate complexes in different valence states. This allowed us to isolate a “single component” self activating Cr(II) complex as well as a rare example of mixed valence Cr(I)/Cr(II) species. Additionally, each of these species acted as switchable catalyst depending on the type of co-catalyst

Catalytic ethylene oligomerization is a well understood industrially viable process. The large majority of scientific literature and patents concerning this process has been developed with the use of chromium catalysts. Commercial systems producing selective tri/tetramerization, non-selective oligomerization and polymerization are all based on this metal with the exception of a few systems based on other transition metals (Zr, Ti, Ni etc.). This versatility raises interesting questions about chromium’s unique behaviour. Essentially, selective or non-selective oligomerization and polymerization processes could be regarded as belonging to the same category of C-C bond forming reactions, though different mechanisms are involved. The first part of this thesis explores a variety of chromium complexes for ethylene oligomerization purposes. In order to gather further information about the unique behaviour of chromium, we have explored a variety of nitrogen and phosphorus containing ligands. We started with a simple bi-dentate anionic amidophosphine (NP) ligand and assessed the role of the ligand’s negative charge and number of donor atoms in determining the type of catalytic behaviour in relation to the metal oxidation state. This ligand proved capable of generating a series of chromium dimeric, tetrameric or polymeric and even heterobimetallic chromium-aluminate complexes in different valence states. This allowed us to isolate a “single component” self activating Cr(II) complex as well as a rare example of mixed valence Cr(I)/Cr(II) species. Additionally, each of these species acted as switchable catalyst depending on the type of co-catalyst

Many zeolites are deployed in various industrial processes owing to their robust catalytic performance and hydrothermal stability. Reactions in zeolites are catalyzed via framework aluminum. The Si/Al ratio is a metric that describes the relative aluminum content in zeolites. However, several researchers noted that the proximity of aluminum in the framework could impact the catalyst output [1–3]. In this work, the influence of paired acid sites is examined in ZSM-22. The 1-dimensional nature of ZSM-22 allows for direct assessment of aluminum proximity without the influence of channel intersection. Theoretical investigations via static density functional theory (DFT) optimization calculations on isolated and paired BAS in ZSM-22 revealed a potential increase in deprotonation potential energy (DPE), indicating a weaker acid with closer aluminum sites. One specific paired model, however, suggested stronger acid behavior, likely due to unfavorable proton-proton interactions influenced by proximity and orientation. Additionally, ammonia adsorption calculations inferred improved adsorption by isolated models, possibly due to unfavorable ammonium-proton interactions in the paired models. Reaction state calculations of ethylene and propylene oligomerization suggested enhanced stabilization of reactant molecules in paired sites. The synthesis of ZSM-22 showed sensitivity to precursor ratios and conditions, but pure samples were successfully achieved through iterative optimization. Catalytic testing of ethylene oligomerization with these samples, classified by their Si/Al ratios and unique fractions of paired acid sites, showed a correlation between higher fractions of paired BAS and increased catalytic activity and selectivity. Samples with higher fractions of paired BAS displayed a higher activity and selectivity for heavier hydrocarbons, explained by the enhanced adsorption capacity of paired BAS for larger reactant molecules, prompting further oligomerization and enhanced catalytic activity. Our findings demonstrate the impact of BAS proximity in dictating the activity and selectivity in ZSM-22 and provide valuable insights for designing more efficient industrial zeolite-based catalysts.

L’objectif de cette thèse portait sur la synthèse de complexes portant un ligand NHC associé à une fonction oxygénée et à leur application en catalyse d’oligomérisation de l’éthylène. Dans le but de synthétiser des complexes avec des ligands NHCalcool, les complexes d’argent correspondants ont été synthétisés et utilisés en transmétallation. Aucun résultat concluant n’a pu être obtenu avec le nickel à cause de l’acidité du proton alcoolique. Mais un ligand NHC-alcoolate a pu être obtenu par déprotonation directe du pro-ligand avec une base forte. Il fut alors possible d’accéder à des complexes de nickel polynucléaires, certains incorporant dans leur structure des cations lithium provenant de la base utilisée. Par comparaison, des complexes de palladium ont été synthétisés avec des NHCs-alcool ou -alcoolate par réaction des pro-ligands avec Pd(acac)2 suivie de réactions acido-basiques. Etant donné la difficulté d’obtention des complexes de nickel avec des ligands NHC-alcool, la fonction éther a été étudiée. Les complexes résultants ont été testés en oligomérisation de l’éthylène. / The purpose of this work was the synthesis of complexes bearing O-functionalized NHC ligands in order to test their catalytic properties in ethylene oligomerization. In order to have access to alcohol-functionalized complexes, the corresponding silver complexes were synthesized for transmetallation purpose. Whereas no concluding results were obtained with the alcohol function in association with nickel, it was possible to access an alcoholate-functionalized NHC ligand by deprotonation of the corresponding pro-ligand. Thus, polynuclear nickel complexes were prepared, some of them included in their structure a lithium cation originating from the base. For comparison, alcohol- and alcoholate-functionalized NHC palladium complexes were synthesized by direct reaction of the pro-ligand with Pd(acac)2 followed by acidobasic reactions. Because of the complexity of the chemistry of NHC-alcohol ligands associated with nickel, the ether functionality was explored. A library of nickel complexes was synthesized and tested in the catalytic ethylene oligomerization.

Des ligands hydrides potentiellement bidentes (possédant un donneur N-hétérocyclique (NHC) associé à un groupement donneur éther ou amine) ainsi que des ligands tritopiques de type pinceur (possédant un groupement (NHC) flanqué de deux types de donneurs azotés différents Nimine et Namine) ont été préparés et utilisés pour la coordination de métaux de transition tels que le Ni, Cr, Cu et Ir. L’influence de la longueur de la chaine alkylée -(CH2)2- ou -(CH2)3- reliant le groupe éther ou amine au groupe hétérocyclique (NHC) a été examinée. Dans le but d’accéder aux complexes des métaux de transition différentes méthodologies ont été adoptées : a) déprotonation préalable du sel d’imidazolium suivie de l’addition des précurseurs métalliques correspondants ; b) transmétallation à partir des complexes (NHC) de l’argent correspondants ; c) réaction d’addition oxydante des sels d’imidazolium ou de leurs sels protonés avec du Ni(0). Une série de complexes du Ni(II) et du Cr(III) a été testée dans la réaction catalytique d’oligomérisation de l’éthylène. / Potentially bidentate hybrid ligands (containing a NHC donor associated with an ether or an amine) and tridentate NCN pincer-type ligands (containing a central NHC donor flancked by two chemically-different nitrogen donors (Nimine and Namine)) have been prepared and used for coordination to transition metals, such as Ni, Cr, Cu, Ir. The influence of the length of the alkyl chain, -(CH2)2- or -(CH2)3- connecting the ether or the amine group to the heterocycle NHC was examined. In order to have access to the transition metal complexes, several methodologies were adopted: a) deprotonation of the corresponding imidazolium salts followed by addition of transition metal precursors; b) transmetalation from NHC silver complexes; c) oxidative-addition reaction of Ni(0) with imidazolium salts or the corresponding protonated salts. A series of Ni(II), Cr(III) complexes were tested in the catalytic ethylene oligomerization reaction.