Introduction The chemistry of transitional metal complexes bearing σ-bonded H−X (X = H, Si, C) species/fragments, the so called σ-complexes, are key intermediates in catalytic processes such as hydrogenation, hydrosilylation, alkane functionalization etc. Particularly, the σ-H2 complexes form the best-known group of σ-complexes in which H2 is bound to the metal center in η2-fashion. Several well characterized examples of η2-silane and η2-borane complexes have also been reported. Moreover, in recent years, the carbon analogues of these complexes in which alkanes are coordinated through η2-C-H bonds to the metal center have been attracting the attention of organometallic chemists. An approach towards direct functionalization of σ-bonds in simple alkanes is the heterolytic activation of the C−H bond using highly electrophilic complexes. After all, for fine catalyst design and the selective functionalization of H−H, silanes or simple alkanes, it is necessary to understand the bonding nature of these σ-complexes in depth. Objectives The objectives of this work are as follows a) An attempt to stabilize and gain insights into the bonding nature and reactivity behavior of various sigma ligands on ruthenium center [Ru(η2-HX)(Tpms)(PPh3)2][OTf], (X = H, SiR (R = Me3 or Me2Ph) and CH3). b) Synthesis, characterization and reactivity studies of electrophilic ruthenium(II) complexes bearing (C6F5)2PCH2CH2P(C6F5)2 (dfppe) ligand towards heterolysis of H2. c) An approach towards preparation of insoluble molecular clusters from [Ru(P(OH)3)(dppe)2][OTf]2 complex and Zn, Cd and Cu acetates to realize σ-bond activation under heterogeneous conditions. Significant results In our attempts to gain insights into the bonding nature and reactivity behavior of σ-H2, silane and methane complexes, we followed two strategies to generate these complexes in solution. First, we synthesized and well characterized two new Ru(II)-complexes [RuH(Tpms)(PPh3)2] and [Ru(OTf)(Tpms)(PPh3)2], (OTf = trifluoromethane sulfonate) where Ru-H and Ru-OTf are the key reactive centers, followed by their subsequent reactions with electrophilic reagents such as HOTf, Me3SiOTf and CH3OTf and with H2, PhMe2SiH and CH4 at low temperature, respectively. These reactions finally resulted in the characterization of σ-H2 and σ-silane complexes, however, no σ-methane complex was observed even at low temperature (Scheme 1). Scheme 1 In order to realize highly eletrophilic metal complexes, a chelating fluorinated phosphine ligand 1,2-bis-(pentafluorophenylphosphino)ethane, (C6F5)2PCH2CH2P(C6F5)2 (dfppe) was employed and the synthesis and structural characterization of a series of new, Ru(II) hydride complexes [RuH(P(OMe)3)(bpy)(dfppe)][OTf], cis-[RuH2(dfppe)(PPh3)2] and [RuH(CO)Cl(PPh3)(dfppe)] were accomplished. Protonation reaction of the hydride complexes [RuH(P(OMe)3)(bpy)(dfppe)][OTf] (Scheme 2) and [RuH(CO)Cl(PPh3)(dfppe)] (Scheme 3) with HOTf at low temperature gave free H2 and five-coordinate species [Ru(P(OMe)3)(bpy)(dfppe)][OTf]2 and [Ru(CO)Cl(PPh3)(dfppe)][OTf], respectively. Surprisingly, in all these reactions, dihydrogen complexes are formed which were unobservable in which the H2 ligand was found to be highly labile. Reaction of is-[Ru(bpy)(dfppe)(OH2)(P(OMe)3)][OTf]2 with H2 however, resulted in the heterolytic activation of the H–H bond and concomitant protonation of H2O to give the corresponding hydride complex cis-[Ru(H)(bpy)(dfppe)(P(OMe)3)][OTf] and H3O+ (Scheme 2) . Scheme 2 Scheme 3 In an attempt to prepare insoluble molecular clusters in order to realize σ-bond activation under heterogeneous conditions, we studied the reactivity of highly electrophilic [Ru(P(OH)3)(dppe)2]2+ (dppe = (C6H5)2PCH2CH2P(C6H5)2) complex with various metal acetates. Usage of Zn(OAc)2.2H2O afforded a novel [Ru2(dppe)4P2(OH)2O4Zn2(OAc)(DMP)(OTf)][OTf]2 (Ru-Zn ) soluble bimetallic complex (Scheme 4) which was characterized in detail by NMR and single crystal X-ray crystallography. To achieve the expected insoluble molecular cluster further studies are required to tune the electronics and the sterics around the phosphorous acid moiety. Scheme 4

We describe an iron-catalyzed asymmetric oxidative C−C coupling of diarylamines which proceeds at room temperature with air as final oxidant. Using hexadecafluorophthalocyanine-iron(II) as catalyst in the presence of catalytic amounts of an axially chiral biaryl phosphoric acid, the resulting chiral 2,2′-diamino-1,1′-biaryls are obtained in up to 90 % ee as confirmed by chiral HPLC. A detailed mechanism has been proposed with a radical cation-chiral phosphate ion pair as key intermediate leading to the observed asymmetric induction.

Die vorliegende Arbeit beschäftigt sich mit der Stabilisierung von SFx- (x = 2-3) und SOyFz-Liganden (y, z = 1-2) in der Koordinationssphäre von Platinkomplexen, die den N-heterozyklischen Carben- (NHC)-Liganden 1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolinyliden (IMes) besitzen. Die Synthese des SF3-Komplexes trans-[Pt(F)(SF3)(IMes)2] gelang durch Umsetzung von [Pt(IMes)2] mit SF4 oder SF6. Bei der SF6-Aktivierungsreaktion kam es zur Bildung von zusätzlichen fluorierten Nebenprodukten, welche durch den Vergleich mit den jeweiligen unabhängig synthetisierten Verbindungen charakterisiert wurden. Die starke Neigung zur Hydrolyse der SF3-Einheit bei Kontakt mit H2O führte zur Bildung von trans-[Pt(F)(SOF)(IMes)2]. Eine alternative Darstellung des S(=O)F-Komplexes konnte durch Umsatz von [Pt(IMes)2] mit SOF2 erreicht werden. Die S(=O)2F-Komplexe trans-[Pt(X)(SO2F)(IMes)2] (X = F, Cl) mit dem Schwefel in der formalen Oxidationsstufe IV wurden durch die Behandlung von [Pt(IMes)2] mit SO2F2 oder SO2ClF erhalten. Die Oxidation des S(=O)F- zum S(=O)2F-Liganden konnte durch Behandlung mit dem Oxygenierungsreagenz 3-Phenyl-2-(phenylsulfonyl)-oxaziridin (Oxaz) bewerkstelligt werden. Eine Oxidation und zugleich Fluorierung der S(=O)F-Einheit in trans-[Pt(F)(SOF)(IMes)2] wurde durch Behandlung mit XeF2 durchgeführt, wobei ein S(=O)F2-Ligand in trans-[Pt(F)(SOF2)(IMes)2]F(HF)n erhalten wurde. Reaktionen von trans-[Pt(F)(SF3)(IMes)2] mit der Lewis-Säure AsF5 oder einer HF-Quelle lässt die Generierung des SF2-Liganden als Teil der kationischen Komplexe trans-[Pt(F)(SF2)(IMes)2]X (X = F(HF)n-, As2F11-) zu. Eine vergleichbare Reaktivität wurde für trans-[Pt(F)(SO2F)(IMes)2] gefunden, wenn NaBArF4 (BArF4- = Tetrakis-[(3,5-trifluoromethyl)phenyl]borat) oder eine HF-Quelle eingesetzt wurden und infolge einer Fluoridabstraktion die Bildung eines SO2-Liganden in trans-[Pt(F)(SO2)(IMes)2]X (X = F(HF)n-, BArF4-) beobachtet wurde. / This work deals with the stabilisation of SFx- (x = 2-3) and SOyFz entities (y, z = 1-2) in the coordination sphere of platinum complexes bearing the N-heterocyclic carbene (NHC) ligand 1,3-bis(2,4,6-trimethylphenyl) 2-imidazolinylidine (IMes). The synthesis of the SF3 complex trans-[Pt(F)(SF3)(IMes)2] was achieved by converting [Pt(IMes)2] with SF4 or SF6. During the SF6 activation additional fluorinated by-products were formed that were characterised by the comparison with independently synthesised compounds. The strong tendency of the SF3 entity to hydrolyse in contact with H2O led to the formation of trans-[Pt(F)(SOF)(IMes)2]. An alternative synthesis of the S(=O)F complex was done by reaction of [Pt(IMes)2] with SOF2. The S(=O)2F complexes trans-[Pt(X)(SO2F)(IMes)2] (X = F, Cl) bearing sulfur ligands in the formal oxidation state IV were accessed by treatment of [Pt(IMes)2] with SO2F2 or SO2ClF. The oxidation of the S(=O)F to the S(=O)2F ligand was achieved by treatment with the oxygenating reagent 3-phenyl 2-(phenylsulfonyl) oxaziridine (Oxaz). An oxidation and fluorination of the S(=O)F group at the same time was done by treatment of trans-[Pt(F)(SOF)(IMes)2] with XeF2 to yield a S(=O)F2 ligand in trans-[Pt(F)(SOF2)(IMes)2]F(HF)n. Reactions of trans-[Pt(F)(SF3)(IMes)2] with the Lewis acid AsF5 or an HF source led to the generation of a SF2 ligand in trans-[Pt(F)(SF2)(IMes)2]X (X = F(HF)n-, As2F11-). A comparable reactivity was found for trans-[Pt(F)(SO2F)(IMes)2], when treated with NaBArF4 (BArF4- = tetrakis-[(3,5-trifluoromethyl)phenyl]borat) or an HF source to yield a SO2 ligand in trans-[Pt(F)(SO2)(IMes)2]X (X = F(HF)n-, BArF4-) by fluoride abstraction.

No description available.

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.

Une nouvelle famille de précatalyseurs à base d'lr(lll) a été découverte. La facilité de leur préparation, leur remarquable stabilité, et surtout leur excellente efficacité catalytique dans plusieurs réactions, c.-à-d. la 0-silylation d'alcools, l'hydrosilylation de fonctions CO et CN et l'activation de la liaison C-F, constituent un ensemble de propriétés que d'autres précatalyseurs organométalliques similaires connus à ce jour ne possèdent pas. Le fait le plus significatif est la mise en évidence expérimentale et théorique que les espèces catalytiques impliquées fonctionnement comme une paire de Lewis du type donneur-accepteur [lr(lll)H]-->[SiR3]. Dans ce cas le ligand silylium doit être considéré comme un ligand Z en appliquant le formalisme de Green, ce qui suggère un état d'oxidation formel de +Ill pour l'atome d'iridium. Cette thèse a contribué à une meilleure compréhension de la chimie du silylium appliquée à la chimie organométallique, et a abouti à l'émergence d'un nouveau champ de recherche qui pourra permettre l'élaboration de nouveaux précatalyseurs multicompétents. / A new family of highly active iridacyclic lr(lll) precatalysts has been discovered. Notably, these ionic iridacycles are very stable so that their handling under air whether in solution or as solid powder is possible. The relative simplicity of their molecular structures allows their preparation on gram scale through a very simple and convenient synthetic protocol. We identified important iridium-silane intermediates involved in the catalysis of various reactions, e.g. the 0-silylation of alcohols, the hydrosilylation of CO and CN functions, and the activation of the C(sp3)-F bond of fluorocarbons. Experimental and theoretical studies of these intermediates point towards a Lewis donor-acceptor structural formulation of the type [lr(lll)H]-->[SiR3]. These results constitute a significant contribution to the design of future multicompetent precatalysts, and provide an original insight to the bonding within the Si-lr-H motif by considering the silylium ion [SiR3]+ as a Z-type ligand rather than a "traditional" X ligand.

No description available.

Unprecedented Ullmann couplings of murrayafoline-A with either 6-bromo- or 4-bromocarbazole derivatives provide highly efficient synthetic routes to the biscarbazole alkaloids murrastifoline-A (6 steps, 66% overall yield) and bismurrayafoline-A (6 steps, 28% overall yield). / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Unprecedented Ullmann couplings of murrayafoline-A with either 6-bromo- or 4-bromocarbazole derivatives provide highly efficient synthetic routes to the biscarbazole alkaloids murrastifoline-A (6 steps, 66% overall yield) and bismurrayafoline-A (6 steps, 28% overall yield). / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.