Cette thèse porte sur l’étude de nouveaux carbènes N-hétérocycliques dont les atomes d'azote sont substitués par des groupes étendus alkylfluorényle (AF). Les caractéristiques principales de ces coordinats sont leur fort encombrement stérique, la modularité de ce dernier, et la proximité créée dans les complexes correspondants entre les groupes AF et le métal coordiné.La première partie de ce travail décrit la synthèse et la caractérisation d'un ensemble de sels d’azolium, précurseurs de cette nouvelle famille de NHCs. Ces composés ont d'abord été utilisés pour la préparation de complexes de palladium de type "Pd-PEPPSI-NHC", complexes qui se sont avérés très efficaces en couplage de Suzuki-Miyaura entre acides arylboroniques et chlorures d’aryle para-substitués. Des études structurales et RMN ont montré que dans leur complexes, les NHC formés agissent comme des pinces bimodales, c'est-à-dire combinant une interaction covalente (la liaison M-Carbène) et deux interactions non-covalentes impliquant les groupes AF. Dans certains complexes linéaires de l’or(I) et du cuivre (I), ces interactions faibles entre le métal et des liaisons C-H alentours ont permis la coordination non-optimale du centre métallique qui, à l’état solide, se retrouve hors de l’axe formé par le doublet non liant du carbène. Enfin, un complexe de type CuCl(NHC) dont l’encombrement stérique est variable a été préparé. Il s’est avéré être un excellent catalyseur d’hydrosilylation d’aldéhydes et de cétones. A ce jour, il possède l’une des plus grandes activité et longévité (TONs jusqu’à 1000) pour ce type de complexe / This thesis deals with a series of N-heterocyclic carbene ligands (NHCs) in which the N atoms bear expanded alkylfluorenyl (AF) substituents. Special focus has been put on the steric properties of these new ligands, as well as their influence on catalytic reactions involving Pd and Cu centres.The first part of this work describes the synthesis of a series of AF-substituted azolium salts suitable for the preparation of palladium PEPPSI-NHC complexes. These turned out to be very active in Suzuki-Miyaura cross-coupling reactions between para-substituted aryl chlorides and arylboronic acids. Structural and NMR studies revealed that in all the complexes, the NHC ligand displays a "bimodal pincer" type behaviour, that is functions as a tridentate ligand bound to the metal through both covalent and non covalent bonds, the former involving the carbenic C atom, the latter CH atoms of the wingtips.In the second part of the study, a series of linear [AuCl(NHC)] and [CuCl(NHC)] complexes were prepared. In some of them were observed weak CH•••M interactions involving the alkyl chains fixing the metal centre in a position below the NHC ring plane. This leads to an unusual coordination of the ligand able to freeze out the movement of the metal centre during its natural oscillation about the M-carbene axis.In the last part of this thesis, one of the [CuCl(NHC)] complexes synthesised was shown to be highly efficient in the catalytic hydrosilylation of functionalised/sterically crowded aldehydes and ketones (TONs up to 1000). Its high stability was attributed to the variable encumbrance of the ligand.

Les nanomatériaux ont beaucoup captivé l'attention pour leur propriétés uniques, fortement associées à leurs dimensions nanoscopiques. En particulier, les nanoparticules (NP) à base de métaux nobles (Au, Ag) présentent des propriétés mécaniques, électroniques, optiques et magnétiques particulières intéressantes pour le développement d'applications dans de nombreux domaines à fort impact sociétal. En raison de leur stabilité élevée par rapport aux autres nano- particules métalliques, les nanoparticules d'or ont été abondamment explorées pour les nanotechnologies. Ces dernières décennies, les NHC ont émergé en tant que classe essentielle de ligands neutres en chimie organométallique. Les NHC sont caractérisés par leur flexibilité synthétique élevée, leur géométrie spécifique, et une liaison métal–Ccarbène très forte dans les complexes métalliques. Toutes ces propriétés ont été largement étudiées et exploitées pour les applications en catalyse homogène et pour le développement de complexes biologiquement actifs. Par comparaison, l'utilisation des NHC dans les matériaux reste largement peu explorée. Dans ce travail, le potentiel de ligands NHC dans le domaine des nanomatériaux, comme des agents de revêtement pour le produit nanocristaux de synthèse de l'or (et l'argent), la produit de stabilisation et de l'auto-assemblage dans supracrystals ont été explorés. Tout d'abord, des complexes d'argent et d'or-NHC qui sont bien définies avec différents ligands qui sont connus comme le NHC, sont étudiés pour leur pertinence afin de générer des astable nanocristaux (NCs) dans des conditions réductrices avec un bon contrôle de la taille des nanocristaux. Nous démontrons que le Au et le Ag NCs peuvent tous être formés par la réduction des complexes métal-NHC avec les amine-boranes. L'efficacité du procédé, la taille moyenne et la taille de la répartition des nanocristaux dépendent fortement de la structure du ligand NHC. Cependant, nous démontrons dans cette partie que les différentes voies sont impliqués à générer des nanocristaux par Au ou Ag précurseurs, comme une spécifique réaction observée entre Ag-NHC et thiols conduisant à la formation de thiolates argent alors que le Au-NHC correspondant reste inchangé... / Nanomaterials have received extraordinary attention owing to their unique properties, strongly associated to their nanoscale dimensions. In particular, noble metal (Au, Ag) nanoparticles (NPs) exhibit particular mechanical, electronic, optical and magnetic properties and present a high potential for developing applications in many domains with important societal impacts. Due to their higher stability by comparison with other metal-based nanoparticles, Au NPs have been extensively investigated for research in nanotechnology. In the last decades, N-Heterocyclic carbenes (NHCs) have emerged as an essential class of neutral ligands in organometallic chemistry. NHCs are characterized by their high synthetic flexibility, their specific geometry, and a very strong metalCcarbene bond in metal complexes. All these properties have been widely studied and exploited for applications in homogeneous catalysis and for the development of biologically active complexes. By comparison, the use of NHCs in nanomaterials remains largely unexplored. In this work, the potential of NHC ligands in the field of nanomaterials, as coating agents for gold nanocrystals synthesis, stabilization and self-assembly into supracrystals has been explored. First, well-defined silver and gold–NHC complexes with different well-known NHC ligands are investigated for their relevance to generate stable nanocrystals (NCs) under reductive conditions with a good control of nanocrystals size. We demonstrate that both Au and Ag NCs can be formed by reduction of metal-NHC complexes with amine-boranes. The efficiency of the process and the average size and size distribution of the nanocrystals markedly depends on the structure of the NHC ligand. However, we demonstrate in this part that different pathways are involved to generate nanocrystals from Au or Ag precursors, as a specific reaction is observed between Ag-NHCs and thiols leading to the formation of silver thiolates whereas the corresponding Au-NHCs remain unchanged...

Chapter one is an introduction, outlining the structure and bonding of N-heterocyclic carbenes (NHCs). It then goes on to give examples of f -metal NHC complexes and describes any reactivity or catalytic activity. Chapter two describes the synthesis of the transition metal NHC complexes [Fe (LMes)2] 3 and [Co(LMes)2] 4 (LMes = OCMe2 CH2(1-C{NCH2CH2NMes})). The heterobimetallic complexes [(LMes)Fe(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(Si Me3)2)2] 5 and [(LMes)Co(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(SiMe3)2)2] 6 were prepared from the reaction between [({Me3Si}2N)2U(NSiMe3SiMe2CH2)] and 3 or 4, respectively. Complex 5 was also synthesised by the reaction between 3 and [U(N{SiMe3}2)2]. The diamagnetic analogue [(LMes)Zn(μ-LMes)Th(μ-{N(SiMe3)Si (Me)2CH2})(N(SiMe3)2)2] 9 was prepared from the reaction between [Zn(LMes)2] and [({SiMe3}2N)2Th(NSiMe3SiMe2CH2)]. The reactivity of 5 is discussed. When 5 was reacted with 2,6-dimethylphenyl isocyanide, [({SiMe3}2N)2U{N(SiMe3)Si(Me2)C(CH2)N(2,6−Me−C6H3)}] 8 was isolated. The reaction with CO resulted in the formation of [({Me3Si}2N)2U{N(SiMe3) Si(Me2)C(CH2)CO}]. 5 showed no reactivity with azides, boranes or m-chloroperbenzoic acid and decomposed when exposed to H2, CO2 or KC8. The reaction between 6 and 2,6-di-tert-butylphenol formed the previously reported monometallic complex [({SiMe3}2N)2U(OC6H3tBu2)]. The serendipitous synthesis of the iron ate complex [Na(Fe{LMes}2)2]+ [Fe(ArO)3]– 10 (Ar = 2,6-tBu-C6H3) is also described. Chapter three describes the synthesis of the aryloxide complexes [HC(3-tBu-5-Me- C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Co(THF)]2 11 and [HC(3- tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Zn(THF)n] 13. Treatment of 11 with pyridine N-oxide resulted in the formation of the pyridine-Noxide adduct [HC(3-tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2 O)Co(C5H5NO)]2 12. When 11 was treated with [({Me3Si}2N)2U(NSiMe3SiMe2C H2)], no reaction occured at room temperature but at 80◦C decomposition occured. When 11 was treated with [(NH4)2Ce(NO3)6] the protonated proligand HC(3-tBu- 5-Me-C6H2OH)3 reformed. The reactivity of 11 with [({Me3Si}2N)Ce(LiPr)2] is also discussed. Chapter three also discusses the preparation of the heterobimetallic complex [HC(3- tBu-5-Me-C6H2O)2-μ-(3-tBu-5-Me-C6H2O)KCo]2 14 and the salt-elimination chemistry of the complex. The preparation of [HC(3-tBu-5-Me-C6H2O)2-μ-(3-tBu-5- Me-C6H2O)KZn]2 15 is also outlined. Chapter four discusses the reactivity of [Ce(LiPr)3] (Li Pr =OCMe2CH2(1-C{NCHC HNiPr})) in C-H and N-H activation and as a catalyst for organic reactions. [Ce(LiPr)3] displayed no C-H activation chemistry with RC−−−CH (R = SiMe3, Ph, tBu), diphenyl acetone, indene or fluorene. [Ce(LiPr)3] also showed no N-H activation chemistry with pyrrole or indole, nor did it react with the lignin model compound PhOCH2Ph. When treated with an excess of benzyl chloride, [Ce(LiPr)3] underwent ligand decomposition to form the acylazolium chloride [(C6H5C(O))OCMe2CH2(1-C(C6H5C (O)){NCHCHNiPr})]Cl 18 and CeCl3. When [Ce(LiPr)3] was added to a mixture of benzaldehyde and benzyl chloride, as a coupling catalyst, the complex decomposed. [Ce(LiPr)4] was tested as a catalyst from the benzoin condensation and for the coupling of benzalehyde and benzyl chloride, however, it resulted in the decomposition of [Ce(LiPr)4]. Chapter four also outlines the catalytic activity of 3. The complex showed no reactivity as a hydrogenation catalyst towards alkenes, aldehydes or ketones but did display reactivity as a hydroboration catalyst for alkenes, aldehydes or ketones. Chapter five presents the conclusions for chapters two to four. The final chapter contains the experimental details from the previous chapters.

Ces travaux de thèse se partage en deux parties distinctes : d’une part, les travaux concernant l’insertion du cobalt dans la liaison C(O)–N d’amide non-planaire, et les réactions de catalyse qui en découlent, et d’autre part, le développement d’une nouvelle famille de complexes de cobalt, basé sur ligand 5-(4-pyridyl)dipyrrométhène et ses dérivés. Dans la première partie, qui concerne la catalyse au cobalt avec les dérivés d’amides, la réactivité de différents sels et complexes de cobalt avec les amides non-planaires a été étudiés. L’insertion du cobalt se fait en présence de bipyridine en tant que ligand, dans le DMF, avec du manganèse métallique en tant que système réducteur. L’optimisation des réactions de conversion des amides secondaires en esters et les couplages réducteurs entre amides et iodoaryles est ensuite décrite.Dans la seconde partie, concernant la chimie de coordination du cobalt, le développement de complexes cobalt-dipyrrométhène est présenté. Dans un premier temps, l’optimisation de la synthèse des 5-(4pyridyl)dipyrrométhène décrite, suivi de tests de complexation avec différents précurseurs de cobalt. Le ligand ayant deux sites de coordination, la coordination sélective d’un métal de transition sur un des sites dépends principalement de l’encombrement du site "dipyrrométhène”. Si ce site est suffisamment encombré, le cobalt se chélate préférentiellementsur la partie pyridine. Pour forcer la coordination du cobalt dans la partie dirpyrrin, il est nécessaire de bloquer la partie pyridyl. En coordinant un précurseur de ruthénium photosensible sur la pyridine avant le cobalt, il est possbile d’obtenir un complexe bimétallique cobalt-ruthenium, permettant la photoréduction du cobalt, et donc potentiellement le développement d’une catalyse au cobalt sans réducteur métallique. / This thesis is divided in two distinct part: on one side, the works concerning the cobalt insertion into the C(O)–N bond of non-planar amides, and the resulting reactions, and on the other side, the development of a new family of cobalt complexes, based on the 5-(4-pyridyl)dipyrromethene ligand and its derivatives.In the first part, concerning cobalt catalysis with amide derivatives, the reactivity of different cobalt precursors and complexes toward non-planar amides has been studied. The insertion of the cobalt can be realized in presence of bipyridine as ligand, en DMF, with manganese powder as reductant system. The otpimization of the amide-to-ester conversion and the reductive cross-coupling between amides and iodo-aryl is then described.In the second part, concerning the coordination chemistry of cobalt, the development of cobalt-dipyrromethene complexes is presented. Firstly, the optimization of the 5-(4-pyridyl)dipyrromethene synthesis is described,followed by complexation tests with different cobalt precursors. With two coordination sites on the ligand, the selective coordination of a transition metal on one of the sites depends mainly on the dipyrrin hindrance. If this part is hindered enough, cobalt chelate preferentially on the pyridyl part. To force the cobalt coordination on the dipyrrin part, it is necessary to occupied the pyridyl part. By coordinating a photoensitive ruthenium precursor on the pyridine, it is possible to obtain un bimetallic cobalt-ruthenium complex, allowing the cobalt photoreduction, and potentially the development of a cobalt catalysis without metallic reductant.

With its unrivaled versatility and atom economy, olefin metathesis is arguably the most powerful catalyst methodology now known for the construction of carbon-carbon bonds. When compared to palladium-catalyzed cross-coupling methodologies, however, catalyst productivity lags far behind, even for the “robust” ruthenium metathesis catalysts. Unexpected limitations to the robustness of these catalysts were first widely publicized by reports describing the implementation of metathesis in pharmaceutical manufacturing. Recurring discussion centered on low catalyst productivity resulting from decomposition of the Ru catalysts by impurities, including ppm-level contaminants in the technical-grade solvent. Over the past 7 years, a series of mechanistic studies from the Fogg group has uncovered the pathways by which common contaminants (or indeed reagents) trigger catalyst decomposition. Two principal pathways were identified: abstraction of the alkylidene or methylidene ligand by nucleophiles, and deprotonation of the metallacyclobutane intermediate by Bronsted base. Emerging applications, however, notably in chemical biology, highlight new challenges to catalyst productivity. The first part of this thesis emphasizes the need for informed mechanistic insight as a guide to catalyst redesign. The widespread observation of a cyclometallated N-heterocyclic carbene (NHC) motif in crystal structures of catalyst decomposition products led to the presumption that activation of a C-H bond in the NHC ligand initiates catalyst decomposition. Reducing NHC bulk has therefore been proposed as critical to catalyst redesign. In experiments designed to probe the viability of this solution, the small NHC ligand IMe4 (tetramethylimidazol-2-ylidene) was added to the resting-state methylidene complexes formed in metathesis by the first- and second-generation Grubbs catalysts (RuCl2(PCy3)2(=CH2) GIm or RuCl2(H2IMes)(PCy3)(=CH2) GIIm, respectively). The intended product, a resting-state methylidene species bearing a truncated NHC, was not formed, owing to immediate loss of the methylidene ligand. Methylidene loss is now shown to result from nucleophilic attack by the NHC – a small, highly potent nucleophile – on the methylidene. Density functional calculations indicate that IMe4 abstracts the methylidene, generating the N-heterocyclic olefin H2C=IMe4. The latter is an even more potent nucleophile, which attacks a second methylidene, resulting in liberation of [EtIMe4]Cl. These findings report indirectly on the original question concerning the impact of ligand truncation. The ease with which a small, potent nucleophile can abstract the key methylidene ligand from GIm and GIIm underscores the importance of increasing steric protection at the [Ru]=CH2 site. This chemistry also suggests intriguing possibilities for efficient, selective, controlled methylidene abstraction to terminate metathesis activity while leaving the “RuCl2(H2IMes)(PCy3)” core intact. This could prove an enabling strategy for tandem catalysis applications in which metathesis is the first step. The second part of this thesis, inspired by the potential of olefin metathesis in chemical biology, focuses on the impact of hydroxide ion and water on the productivity of phosphine-free metathesis catalysts. In reactions with the important second-generation Hoveyda catalyst HII, hydroxide anion is found to engage in salt metathesis with the chloride ligands, rather than nucleophilic attack. The resulting Ru-hydroxide complex is unreactive toward any olefins larger than ethylene, while ethylene itself causes rapid decomposition. Proposed as the decomposition pathway is bimolecular coupling promoted by the strong H-bonding character of the hydroxide ligands. Lastly, the impact of the water on Ru-catalyzed olefin metathesis is examined. In a survey of normally facile metathesis reactions using state-of-the-art catalysts, even trace water (0.1% v/v) is found to be highly detrimental. The impact of water is shown to be greater at room temperature than previously established at 60 °C. Preliminary evidence strongly suggests that the mechanism by which water induces decomposition is temperature-dependent. Thus, at high temperature, decomposition of the metallacyclobutane intermediate appears to dominate, but this pathway is ruled out at ambient temperatures. Instead, water is proposed to promote bimolecular decomposition. Polyphenol resin, which can sequester water by H-bonding, is shown to offer an interim solution to the presence of trace water in organic media. These findings suggest that major avenues of investigation aimed at reducing intrinsic catalyst decomposition may likewise be relevant to the development of water-tolerant catalysts.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18093号 / 理博第3971号 / 新制||理||1572(附属図書館) / 30951 / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 丸岡 啓二, 教授 時任 宣博 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21120号 / 工博第4484号 / 新制||工||1697(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 大江 浩一, 教授 辻 康之, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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No description available.

Transition metal catalysis is a necessary branch of organic synthesis. Both monometallic and bimetallic catalysts can reduce reaction times, improve regio- and enantioselectivity, and minimize byproducts. Additionally, bimetallic catalysts can cooperatively activate substrates, which can enable new reactions and mechanistic pathways. The first half of this work will describe the synthesis and catalytic ability of our novel Pd(I) and Pd(II) dimers. Both dimers use a 2-phosphinoimidazole ligand scaffold to bring the metal centers in close proximity. The Pd(II) dimer can catalyze the synthesis of 1,3-disubstituted naphthalene rings from commercially available aryl iodides and methyl ketones with high regioselectivity and yields. Mechanistic and theoretical studies suggest the mechanism undergoes a Pd(III)–Pd(III) like intermediate. Additionally, we studied the impact of precatalyst oxidation state on C–N bonding reactions. We found that our Pd(I) dimer performed better in Buchwald-Hartwig aminations, while our Pd(II) dimer was shown to be extremely active in aminocarbonylation reactions. Both reactions gave C–N bonding products in good to excellent yield. The second portion of this work describes our novel Pd N–H NHC complex and its application in Suzuki-Miyaura cross couplings. In the presence of methanol, a Pd(II) salt will insert into the C–P bond of a 2-phosphinoimidazole ligand to give a protic NHC complex. The acidic hydrogen can be deprotonated under reaction conditions to give an anionic complex, which further increases the electron density on palladium as shown in Tolman Electronic Parameter studies. Application of the catalyst in Suzuki-Miyaura and Sonogashira coupling reactions gave product in high yield. Since our Pd N–H NHC complex with a diphenylphosphine ligand could not activate aryl chlorides, we then applied 2-dialkylphopshinoimidazole ligands. When the dialkyl ligands were stirred with Pd(II) salts in methanol, an equilibrium was observed between N–H NHC and P–N coordination complexes. When the catalytic mixture was applied to Suzuki-Miyaura cross-couplings, (hetero)aryl chlorides gave high yields with low catalyst loadings.