La molécule de méthane possède la liaison C-H la plus forte parmi les hydrocarbures (BDE = 104 kcal mol-1) : son oxydation en conditions douces représente un challenge d'importance. La Méthane Monoxygénase particulaire (pMMO) est une enzyme à cuivre qui catalyse l'oxydation du méthane (CH4) en méthanol (CH3OH). Le site actif de l'enzyme est composé d'atomes de cuivre séparés par 2.6 Å. Des recherches récentes suggèrent qu'un cluster Cu2 III,II/O2 à valence mixte soit un intermédiaire-clé du cycle catalytique. L'objectif de ce travail vise à la synthèse et caractérisation de nouveaux complexes dinucléaires à valence mixte de type bis(µ-oxo)Cu2 III,II ou (µ-OH, µ-O)Cu2 III,II. Deux familles de motifs coordinants ont été mises en oeuvre, polypyridyle ou polyamide ; les deux sites sont assemblés par des ponts courts et rigides, phenoxo, naphthyridine ou alkoxo. De nouveaux complexes ont été caractérisés par électrochimie, spectroscopies UV-visible et RPE, et par des calculs théoriques. Un dispositif original de cryo-spectroélectrochimie UV-vis-NIR a été développé en parallèle de cette étude : il permet l'identification spectroscopique d'intermédiaires transitoires, réputés très instables à température ambiante. De nouveaux composés à valence mixte, Cu2 III,II(μ-OH, μ-O) et Cu2 III,IIbis(μ-OH) ont été identifiés. Ces résultats élargissent le champ des données de cette famille d'intermédiaires instables limitée jusqu'ici à un seul exemple. / Methane has the strongest C-H bond of any hydrocarbon (BDE = 104 kcal mol-1); its oxidation under mild conditions remains a great challenge. The particulate Methane Monooxygenase (pMMO) is a copper enzyme that oxides methane (CH4) to methanol (CH3OH). In the active site of the enzyme, two copper ions are located at a short distance (2.6 Å). Recent researches have suggested a mixed-valent Cu2III,II/O2 cluster as a key intermediate in the catalytic cycle. The main objective of this work was the synthesis and characterization of new mixed-valent CuIIICuII bis(μ-oxo) and (μ-OH, μ-O) dinuclear complexes. For this purpose we designed promising symmetrical and unsymmetrical complexes based on specific and distinct scaffolds for each side of the structure. Two families of coordination pattern have been used, polypyridyle or polyamide; the two sites are shortly and rigidly bridged by phenoxo, alkoxo or naphthyridine linkers. New complexes have been characterized by electrochemistry, UV-vis and EPR spectroscopies, and by theoretical calculations. A new cryo-UV-Vis-NIR spectroelectrochemical set up, developed in parallel during this work, has allowed the spectroscopic identification of these transient intermediate species, known to be unstable at room temperature. New mixed-valence Cu2 III,II(μ-OH, μ-O) and Cu2 III,IIbis(μ-OH) complexes have been characterized. These results expand the recent knowledge on the only mixed valent CuIII(μ-OH)CuII species described so far.

La chiralité axiale est une propriété importante de composés biologiquements actifs, de matériaux avancés et plus particulièrement de ligands utilisés en catalyse asymétrique. En effet de nombreuses structures biaryliques atropisomériques ont montré un excellent pouvoir d’induction asymétrique. Ainsi le contrôle de l’atropisomérie et le développement de nouvelles méthodes synthétiques permettant la synthèse de composés à chiralité axiale optiquement purs attire l’attention de la communauté scientifique. Au cours de ce travail une nouvelle stratégie vers l’obtention de biaryles à chiralité axiale atropenrichis a été explorée. L’utilisation de sulfoxydes énantiopurs, jouant à la fois le rôle de groupe directeur et d’auxiliaire de chiralité, dans une stratégie de fonctionnalisation de liaisons C-H par catalyse homogène au palladium, a permis l’obtention efficace de nombreux composés biaryliques hautement atropenrichis . Les méthodologies développées ont ensuite été appliquées à la synthèse formelle d’un composé naturel bioactif à chiralité axiale, la (-)-steganone, ainsi qu’à la synthèse de ligands doublement atropisomériques inédits. / Axial chirality is an important property of biologically active compounds, advanced materials and more importantly of ligands used in asymmetric catalysis. Indeed, numerous atropisomeric biaryls have demonstrated an excellent asymmetric induction capacity. Thus, the control of atropisomery and the development of original synthetic methodologies allowing the synthesis and the obtention of optically pure axially chiral compounds is an important goal for the scientific community. In this work, a new strategy for the synthesis of atropenriched axially chiral biaryls was explored. The use of enantiopur sulfoxides playing the role of both, a directing group and a chirality auxiliary, in a palladium catalyzed C-H functionalization, allowed the efficient construction of numerous highly atropenriched biaryl compounds. The developed methodologies were furthermore applied to the formal synthesis of an axially chiral and bioactive compound, (-)-steganone, as well as the synthesis of doubly atropisomeric unprecedented ligands. These ligands displayed an excellent potential for asymmetric induction in homogenous asymmetric hydrogenation.

La conception de ligands est d'une grande importance pour le développement de la catalyse métallique, conformément à une approche de chimie durable.La première partie de cette thèse porte sur une revue bibliographique détaillée des ligands phosphorés couramment employés dans les systèmes catalytiques pour les réactions de couplage carbone‒carbone catalysées au palladium. La deuxième partie traite du contrôle conformationnel du squelette ferrocénique dans les ligands polyphosphines. Ce contrôle conformationnel vise à induire des interactions inédites entre deux atomes de phosphore, et également avec des centres métalliques. De nouveaux anions cyclopentadiényles substitués et encombrés ont été synthétisés, et ont permis de réaliser la synthèse de triphosphines ferrocéniques inédites. Les réactions avec le fer (II) des sels d'anions cyclopentadiényles substitués par des groupements encombrés (tertio-butyle, trityle, super-trityle) et des groupements phosphino enrichis ou appauvris en électrons (isopropyle, cyclohexyle, furyle) ont conduit à une série de nouveaux ligands polyphosphines ferrocéniques multidentes. Leurs coordinations à des sels de palladium ou de platine ont été étudiées. Les complexes de coordination correspondants ont été isolés avec de très bons rendements et caractérisés en solution par RMN 1H, 13C, 31P et à l'état solide par Diffraction des Rayons X.La troisième partie décrit la synthèse et la caractérisation de diphosphines ferrocéniques inédites. Des investigations ont été menées en électrochimie sur ces ligands et les propriétés électroniques des dérivés séléniés correspondants ont été étudiées par RMN 31P‒77Se.Ces ligands se sont montrés des auxiliaires efficaces pour l’arylation pallado-catalysée d’hétéroaromatiques dans l’activation C‒H ou dans le couplage C‒O, surtout à faible charge de catalyseur, en accord avec les exigences du développement de chimie durable / The design of ligands is of great importance for the development of metal catalysis, in keeping with an ever more sustainable approach of chemistry.The first part of this thesis focuses on a detailed literature review of phosphorus ligands commonly used in catalytic systems for the coupling reactions catalyzed carbon-carbon palladium.The second part deals with the conformational control of the ferrocene backbone within polyphosphine ligands. This conformational control aims at inducing unedited interactions between phosphorus atoms, and also with metal centers. New substituted and hindered cyclopentadienyl rings were synthesized, which allow the assembling of original ferrocenyl triphosphines. The reactions with iron(II) salts of cyclopentadienyl anions substituted with hindering groups (tert-butyl, trityl, super-trityl) and holding either electron-donor or electron-withdrawing phoshino groups (isopropyl, cyclohexyl, furyl) afford a set of novel multidentate ferrocenyl phosphine ligands. Their coordinations towards palladium and platinum were studied. The corresponding coordination complexes were isolated in high yields and fully characterized in solution by multinuclear 1H, 13C, 31P NMR and in solid state by X-Ray cristallography.The third part describes the synthesis and characterization of original ferrocenyl diphosphines. Electrochemical investigation of these ligands and electronic properties of their corresponding diselenide derivatives by NMR 31P‒77Se coupling constants were studied.These ligands were found efficient auxiliaries for palladium-catalyzed arylation of heteoaromatics through C–H bond activation or C‒O coupling, especially at low loading of catalyst, in agreement with sustainable chemistry development requirement

Significant developments have been made in the field of C–H activation. However, various disadvantages, mainly low reactivity and selectivity, limit their usage in large-scale synthesis. It is crucial to understand the mechanisms and the nature of the transient species involved in the C–H activation paths to develop effective catalytic routes for homogeneous C–H functionalization reactions. Computational techniques are employed in this study to throw light on these processes. Chapter 1 briefly introduces C–H activation and functionalization reactions. After classifying the reactions on the basis of mechanisms, computational studies on the mechanisms of C–H activation reactions are described. The challenges involved in the discovery of efficient homogeneous C–H functionalization catalysts and progress made in the field are discussed. The insights provided to overcome the problems associated with the catalytic C–H functionalization reactions in a few examples are highlighted. In Chapter 2, DFT model studies are carried out to estimate the affinity and selectivity of 16-electron half-sandwich d6-metal fragments (η5–C5H5)Re(CO)2 and (η6–C6H6)W(CO)2 for binding with alkane C–H bonds. Different C–H binding sites of pentane, at the M06 level of theory have been evaluated. The effects of ancillary ligand variations on the metal–pentane binding strength are studied by substituting different ligands such as N-heterocyclic carbene (NHC), PF3 and NO+ for one of the carbonyl ligands. Isomers of the metal-pentane C–H σ-complexes studied in this chapter are shown in Scheme 1. Binding energies of the terminal methyl C–H bonds (C1 and C5) are significantly lower than those of the methylene C–H bonds (C2, C3 and C4) in all the cases. The metal–pentane binding interactions of the rhenium complexes are significantly stronger than those of the corresponding tungsten analogs. The PF3 complexes have slightly greater binding energies compared to the CO complexes, in both Re(I) and W(0) analogs. These results are in conformity with the experimental results. The electron-deficient nitrosyl complexes have the highest binding energies. These results illustrate that by proper tuning of the electronic factors of the transition-metal fragments with different ancillary ligands, the alkane C–H binding affinity can be controlled. Energy decomposition analyses (EDA) are carried out to determine the nature of the interaction between the metal fragments and pentane C–H bonds. Scheme 1. Formation of pentane C–H σ-complexes Chapter 3 addresses the energetics of various intramolecular site-exchange (chain walking) processes and C–H oxidative addition reactions (Scheme 2) of the pentane C–H σ-complexes studied in Chapter 2. Four possible site-exchange processes such as 1,2-, 1,3-, 1,4- and 1,5-migration processes are studied using DFT/M06 level of theory. η2-(H,H)···M type transition states are located for these migrations (Scheme 2). The 1,3-migration is the most favorable process. Two different pentyl hydride isomers, as shown in Scheme 2, are obtained for oxidative addition of methyl and methylene C–H bonds of pentane for all systems, at same level of theory. Oxidative insertion of metal into the methyl C–H bonds is more favorable than insertion into the methylene C–H bonds for all complexes. The activation energies of all site-exchange and C–H oxidative addition processes of the Re(I) complexes are significantly greater than those of the corresponding W(0) complexes. For all these processes, the activation barriers of the electron-deficient NO+ complexes are the greatest among all ligand systems studied, in both Re(I) and W(0) systems. These results are consistent with the experimental results and suggest that the experimentally observed pentyl hydride isomer [(η5–C5H5)Re(CO)(PF3)H(C5H11)] might be Isomer B and not Isomer A (Scheme 2). The C–H oxidative addition reactions are less favorable than dynamic site-exchange processes in all complexes. These results imply that the metal fragments migrate along the pentane chain more easily than insert into the pentane C–H bonds. Scheme 2. Alkane chain walking and C–H oxidative addition reactions Chapter 4 deals with the mechanisms and energetics of a unique metal migration process of an olefin complex that proceeds via olefinic (C–H)···Metal interaction. Migration of the Re(I) fragment from one π face of the olefin to the opposite π face in [(η5–C5H5)Re(NO)(PPh3)(PhCH═CH2)]+ has been documented experimentally by Gladysz and coworkers. The experimental results provide evidences for an intramolecular mechanism for this process (i.e., without styrene dissociation from Re(I)) and based on kinetic isotope effects (KIE), the involvement of a trans C–H bond is indicated. Either oxidative addition or a vinylic (C–H)···Re interaction could account for the experimentally observed kinetic isotope effect. In this study, the free energy of activation for the migration of Re from one enantioface of the olefin to the other through various pathways is computed using DFT calculations at the B3LYP and M06 levels. Two pathways, one that involves migration of Re through a trans (C–H)···Re interaction and another that involves oxidative addition of Re into the trans C–H bond, are identified as possible paths (Scheme 3) at the B3LYP level. Surprisingly, at the M06 level, DFT computes a lower energy path for the conducted tour mechanism that is not consistent with the experimental KIE. But the computed energy profiles for the reaction are consistent with the experiment when computations are carried out at the B3LYP level. Scheme 3. Mechanisms of olefin π face exchange reaction In Chapter 5, the mechanistic studies of C–H metathesis of d6 half-sandwich complex [(η5–C5Me5)Ru(CH3)(CO)(C6H6)] are discussed. A 1-step mechanism that proceeds via a four-center transition state and a 2-step Oxidative Addition and Reductive Coupling mechanism (OA/RC) are identified as possible mechanisms (Scheme 4) using DFT/M06 level of theory. The 1-step mechanism is more favorable than the 2-step mechanism. As in the oxidative addition intermediate, metal–hydrogen bond is observed in the four-center transition state of the 1-step mechanism. This mechanism is referred to as Oxidative Hydrogen Migration (OHM) rather than σ-Bond Metathesis (σ-BM) which proceeds via a transition state without M−H bonding. The effects of metal (M = Fe(II), Ru(II) or Os(II)) and ancillary ligand (L = H–, NHC, CO or NO+) variations on the mechanisms and energetics of the model Cp complex [(η5–C5H5)M(CH3)(L)(C6H6)] are also studied (Scheme 4). Scheme 4. Oxidative hydrogen migration vs Oxidative addition/reductive coupling Increase in the electron-density on the metal center, using electron-donating ligands such as H−, favors the formation of the oxidative species (intermediate or transition state) and reduces the activation barriers of the C–H metathesis reaction. Similarly, the electron-withdrawing NO+ ligand, which reduces the electron density on the metal center, increases the activation energies of the C–H metathesis reaction or disfavors the formation of the oxidative species. Factor affecting the choice of the mechanism of the C–H metathesis reaction is found to be the net charge transfer between the two fragments [(η5–C5H5)M(CH3)(L)] and benzene in [(η5–C5H5)M(CH3)(L)(C6H6)]. The computational studies reported in this thesis provide valuable insight into the mechanisms and energetics of C–H binding, activation and fluxional processes of the (C–H)···Metal σ alkane and alkene complexes. These studies will be helpful in solving problems associated with the C–H activation reactions. Reference Thenraj, M.; Samuelson, A. G. Organometallics 2013, 32, 7141. (For structural formula and figures pl see the abstract pdf file.)

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Die Dissertation beinhaltet Studien zur Reaktivität von Rhodiumkomplexen gegenüber unterschiedlichen ungesättigten fluorierten Olefinen mit einem Fokus auf C–F Aktivierungs- und Borylierungsreaktionen. Der Rhodium(I)hydridokomplex [Rh(H)(PEt3)3] (1) wurde als Katalysator in den Reaktionen von HFO-1234yf, HFO-1234ze, HFO-1225zc bzw. HFO-1225ye (Z) mit HBpin verwendet. Dabei wurden Produktgemische bestehend aus Borylierungsprodukten erhalten. Die selektive Mono- und Dihydroborierung von 3,3,3-Trifluorpropin konnte durch Verwendung von Komplex 1 als Katalysator erreicht werden. Trifluorethylen konnte durch die Reaktion mit HBpin und Komplex 1 als Katalysator in ein Produktgemisch überführt werden. Stöchiometrische Reaktion zeigen, dass Komplex 1 sowohl unter C–F-Bindungsaktivierung reagiert als auch die Koordination von Trifluorethylen, unter Bildung des Komplexes trans-[Rh(F)(ƞ2-CF2CFH)(PEt3)2], stattfindet. Im Falle von 1,1,2-Trifluorbuten wurde ebenfalls eine C–F-Bindungsaktivierung durch Komplex 1 beobachtet. Mechanistische Untersuchungen der Reaktion von Komplex 1 und 1,1,2-Trifluorbuten bei unterschiedlichen Temperaturen zeigten Hinweise für Koordination & Insertion des Alkens, sowie anschließende β-H-Eliminierung und oxidative C–F-Bindungsadditions- und reduktive HF-Eliminierungsschritte. Außerdem konnte durch Verwendung von Komplex 1 oder [Rh(Bpin)(PEt3)3] (3) als Katalysator eine stöchiometrische und katalytische Hydroborierung von Pentafluorstyren mit HBpin erreicht werden. Die Rhodium(I)komplexe 1 und 3 sind in der Lage das Olefin zu koordinieren und die C–F-Bindung zu aktivieren, während die Verwendung der Verbindung [Rh(Me)(PEt3)3] die C–H-Bindungsaktivierung fördert. Bei 333 K findet die Aktivierung des fluorierten Aromaten in der 4-Stellung statt, während bei Raumtemperatur die Aktivierung in der 2-Stellung bevorzugt ist. / The dissertation reports on studies on the reactivity of rhodium complexes towards different fluorinated olefins with a focus on C–F activation steps and borylation reactions. The rhodium(I) hydrido complex [Rh(H)(PEt3)3] (1) was employed as catalyst in the reactions of HFO-1234yf, HFO-1234ze, HFO-1225zc and HFO-1225ye with HBpin. A product mixture consisting of borylation products was obtained. Selective mono and dihydroboration reactions of 3,3,3-trifluoropropyne were achieved by employing complex 1 as the catalyst. Similarly, trifluoroethylene was also converted into a mixture of products by the reaction with HBpin with complex 1 as the catalyst. A stoichiometric reaction of complex 1 resulted in the C–F bond activation as well as a coordination of trifluoroethylene to give complex trans-[Rh(F)(ƞ2-CF2CFH)(PEt3)2]. Furthermore, the C–F bond activation was also realized with complex 1 and 1,1,2-trifluorobutene. Mechanistic investigations of the reaction of complex 1 towards 1,1,2-trifluorobutene at variable temperatures indicated the formation of products of coordination, insertion of the olefin and subsequent β-H elimination, C–F oxidative addition as well as HF reductive elimination steps. Furthermore, when utilizing complex 1 or [Rh(Bpin)(PEt3)3] (3) as catalysts, stoichiometric and catalytic hydroboration reactions of pentafluorostyrene occurred with HBpin. The rhodium(I) complexes 1 and 3 were capable of the coordination of the olefin and a C–F bond activation reaction with pentafluorostyrene, while complex [Rh(Me)(PEt3)3] promoted the C–H bond activation. At 333 K, the activation of the fluorinated aromatic ring occurred at the 4-position, while at room temperature, an activation at the 2-position was preferred.

We describe the oxygenation of tertiary arylamines, and the amination of tertiary arylamines and phenols. The key step of these coupling reactions is an iron-catalyzed oxidative C−O or C−N bond formation which generally provides the corresponding products in high yields and with excellent regioselectivity. The transformations are accomplished using hexadecafluorophthalocyanine−iron(II) (FePcF16) as catalyst in the presence of an acid or a base additive and require only ambient air as sole oxidant.

Catalysis is a key area of chemistry. Through catalysis it is possible to achieve better synthetic routes, exploit molecules normally considered to be inactive and also attain novel chemical transformations. The development of new catalysts is crucial to furthering chemistry as a field. Computational chemistry, arising from applying the equations of quantum and classical mechanics to solving chemical problems, offers an essential route to investigating the underlying atomistic detail of catalysis. In this thesis calculations have been applied towards studying a number of different catalytic processes. The processing of renewable chemical sources via homogeneous reactions, specifically cardanol from cashew nuts, is discussed. All routes examined for monoreduction of a diene model by [Ru(H)(iPrOH)(Cl)(C₆H₆)] and [Ru(H)(iPrOH)(C₆H₆)]⁺ are energetically costly and would allow for total reduction of the diene if they were operating. While this accounts for the need of high temperatures, further work is required to elucidate the true mechanism of this small but surprisingly complex system. Gold-mediated protodecarboxylation was examined in tandem with experiment to find the subtle steric and electronic effects that dictate CO₂ extrusion from gold N-heterocyclic carbene activated benzene-derived carboxylic acids. The origin of a switch in the rate limiting step from decarboxylation to protodeauration with less activated substrates was also clearly demonstrated. Studies of gold systems are closed with examinations of 1,2-difluorobenzene C–H activation and CO₂ insertion by [Au(IPr)(OH)]. Calculations highlight that the proposed mechanism for oxazole-derived substrates cannot be extended to 1,2-difluorobenzene and instead a digold complex offers more congruent predicted kinetics. The lens of quantum chemistry was turned upon palladium-mediated methoxycarbonylation reactions. An extensive study was undertaken to attempt to understand the bidentate diphosphine ligand dependency on forming either methylpropanoate (MePro) or copolymers. Mechanisms currently suggested in literature are shown to be incongruous with the formation of MePro by Pd(OAc)₂ and bulky diphosphines. A possible alternative route is proposed in this thesis. Four mechanisms for methoxycarbonylation with Pd(2-PyPPh₂)ₙ are detailed. The most accessible route is found to be congruent with experimental reports of selectivity, acid dependency and slight steric modifications. A modification of 2-PyPPh₂ to 2-(4-NMe₂-6-Me)PyPPh₂ is shown to improve both selectivity and turnover, the latter by four orders of magnitude (highest transition state from 22.9 kcal/mol to 16.7 kcal/mol ∆G), and this new second generation in silico designed ligand is studied for its applicability to wider substrate scope and different solvents. The final chapter of this thesis is a mixed quantum mechanics and molecular mechanics (QM/MM) examination of an enzymatic reaction, discussing the need for certain conditions and the role of particular amino acid residues in an S[sub]N2 hydrolysis reaction.

Au cours de cette thèse, nous nous sommes intéressés à l'activation de liaisons C-H catalysée par des catalyseurs au palladium pour la préparation de biaryles portant un groupement SO₂R. De très nombreux composés biologiques possèdent une fonction SO₂R. Nous avons donc choisi d'étudier activation de liaisons C-H de ce type de substrat. L'activation de liaisons C-H est considérée comme attractive pour l'environnement par rapport à d'autres types de couplages tels que Suzuki, Stille, ou Negishi. D'abord, nous avons démontré qu'il est possible d'appliquer la méthode d'activation de liaisons C-H pour l'arylation directe de thiophènes portant un substituant SO₂R. Nous avons ensuite établi un système catalysé au palladium pour l'arylation sélective en C2 de dérivés N-tosylpyrrole. Nous avons constaté que le N-tosylpyrrole est plus réactif comparé au pyrrole non protégé. Nous avons également étudié l'arylation directe d'hétéroarènes par des bromobenzènes possédant un substituant SO₂R soit en C2 ou C4 par catalyse au palladium. Cette méthode fournit un accès simple à des dérivés de ArSO₂R. Enfin, nous avons développé la première méthode de déshydrogénation de liaisons sp³ C-H catalysée au palladium de N-alkyl-benzènesulfonamides pour produire des N-alcényle benzènesulfonamides. / During this Ph.D. period, we were interested in the C-H bonds activation catalysed by palladium catalysts for the preparation of biaryls units bearing SO₂R group. Many biological compounds present a SO₂R function and thus we chose to activate this family of substrates. This method is considered as cost effective and environmentally attractive compared to other types of couplings such as Suzuki, Stille, or Negishi. First, we demonstrated that it is possible to apply C-H bond activation method for the direct arylation of thiophene derivatives bearing a SO₂R substituent. We then established palladium-catalysed system for the selective C2 arylation of N-tosylpyrrole derivatives. We found that N-tosylpyrrole is more reactive than free NH-pyrrole. We also studied the direct arylation of heteroarenes using bromobenzenes bearing SO₂R substituents either at C2 or C4 via palladium-catalysed C-H activation. This method provides a simpler access to substituted SO₂R derivatives. Finally we developed the first palladium-catalysed dehydrogenative sp³ C-H bond functionalization/activation of N-alkyl-benzenesulfonamides to produce N-alkenyl-benzenesulfonamides. The reaction proceeds with easily accessible ligand-free Pd(OAc)₂ catalyst for aryl bromides bearing electron-withdrawing groups or PdCl(C₃H₅)(dppb) catalyst for aryl bromides with electron-donating substituents. We found that the reaction tolerates a variety of substituents both on nitrogen and on the bromobenzene moiety.