Bandeau LBPB

Chimie des métaux du groupe 11 (Cu et Au)

  • (P,​C) Cyclometalated Gold(III) Complexes: Highly Active Catalysts for the Hydroarylation of Alkynes
    C. Blons, S. Mallet-Ladeira, A. Amgoune, C. Bourissou
    Angew. Chem. Int. Ed. 2018, 57, 11732-11736

    TOC ACIE Charlie

    The first catalytic application of well‐defined (P,C) cyclometalated gold(III) complexes is reported. The bench‐stable bis(trifluoroacetyl) complexes 2 a,b perform very well in the intermolecular hydroarylation of alkynes. The reaction is broad in scope, it proceeds within few hours at 25 °C at catalytic loadings of 0.1–5 mol %. The electron‐rich arene adds across the C≡C bond with complete regio‐ and stereo‐selectivity. The significance of well‐defined gold(III) complexes and ligand design are highlighted in a powerful but challenging catalytic transformation.

  • Isolation of a Reactive Tricoordinate α-​Oxo Gold Carbene Complex
    A. Zeineddine, F. Rekhroukh, E. D. Sosa Carrizo, S. Mallet-Ladeira, K. Miqueu, A. Amgoune, D. Bourissou
    Angew. Chem. Int. Ed. 2018, 57, 1306-1310

    TOC ACIE Abdallah

    The [(P,P)Au=C(Ph)CO2Et]+ complex 3 [where (P,P) is an o‐carboranyl diphosphine ligand] was prepared by diazo decomposition at −40 °C. It is the first α‐oxo gold carbene complex to be characterized. Its crystallographic structure was determined and DFT calculations have been performed, unraveling the key influence of the chelating (P,P) ligand. The gold center is tricoordinate and the electrophilicity of the carbene center is decreased. Complex 3 mimics transient α‐oxo gold carbenes in a series of catalytic transformations, and provides support for the critical role of electrophilicity in the chemoselectivity of phenol functionalization (O−H vs. C−H insertion).

  • Cyclometalated gold(III) complexes: noticeable differences between (N,​C) and (P,​C) ligands in migratory insertion
    J. Serra, P. Font, E. D. Sosa Carrizo, S. Mallet-Ladeira, S. Massou, T. Parella, K. Miqueu, A. Amgoune, X. Ribas, D. Bourissou
    Chem. Sci. 2018, 9, 3932-3940

    TOC Chem Sci Jordi

    Gold(III) complexes are garnering increasing interest for opto-electronic, therapeutic and catalytic applications. But so far, very little is known about the factors controlling their reactivity and the very influence of the ancillary ligand. This article reports the first comprehensive study on this topic. The reactivity of a cationic (N,C) gold(III) complex, namely 1A, towards ethylene has been thoroughly studied and compared with that of the related (P,C) complex 1C. A cationic gold(III) complex 5A resulting from double insertion of ethylene was selectively obtained. Complex 5A was found to be remarkably stable. It was trapped with chloride and fully characterized. In marked contrast to that observed with 1C, no β-H elimination or linear-to-branched rearrangement of the alkyl chain occurred with 1A. The energy profile for the reactions of 1A with ethylene has been comprehensively investigated computationally, and the influence of the ancillary ligand has been precisely delineated. Because nitrogen is a weaker donor than carbon (and phosphorus), the (N,C) ligand is very electronically dissymmetric, much more than the (P,C) ligand. This makes the two reactive sites at gold quite different, which noticeably influences the competition between migratory insertion and β-H elimination, and actually changes the outcome of the olefin insertion at gold. This study provides valuable insight into the influence of ancillary ligands on gold(III) reactivity, something critical to further develop Au(III) and Au(I)/Au(III) catalysis.

  •  Rational development of catalytic Au(I)​/Au(III) arylation involving mild oxidative addition of aryl halides
    A. Zeineddine, L. Estevez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune, D. Bourissou
    Nature Comm. 2017, 8, 1-8

    TOC Nat Comm 2017 Zeineddine

    The reluctance of gold to achieve oxidative addition reaction is considered as an intrinsic limitation for the development of gold-catalyzed cross-coupling reactions with simple and ubiquitous aryl halide electrophiles. Here, we report the rational construction of a Au(I)/Au(III) catalytic cycle involving a sequence of Csp2–X oxidative addition, Csp2–H auration and reductive elimination, allowing a gold-catalyzed direct arylation of arenes with aryl halides. Key to this discovery is the use of Me-Dalphos, a simple ancillary (P,N) ligand, that allows the bottleneck oxidative addition of aryl iodides and bromides to readily proceed under mild conditions. The hemilabile character of the amino group plays a crucial role in this transformation, as substantiated by density functional theory calculations.

  • Formation of a peri-​Bridged Phosphonio-​Naphthalene by Cu-​Mediated Phosphine-​Aryl Coupling
    C. Blons, M. Duval, D. Delcroix, H. Olivier-Bourbigou, S. Mallet-Ladeira, E. D. Sosa Carrizo, K. Miqueu, A. Amgoune, D. Bourissou
    Chem. Eur. J. 2018, 24, 11922-11925.

    TOC CEJ Phosphonium

    The peri‐iodo naphthyl phosphine 1 reacts with CuI to give the peri‐bridged phosphonio‐naphthalene 2, which has been fully characterized (multi‐nuclear NMR, MS, XRD). The outcome of the reaction differs markedly from that observed with gold. A two‐step pathway involving P‐assisted C−I oxidative addition to copper, followed by P−C reductive elimination is shown to be energetically feasible by DFT calculations.

  • A Nucleophilic Gold(III) Carbene Complex
    A. Pujol, M. Lafage, F. Rekhroukh, N. Saffon-Merceron, A. Amgoune,* D. Bourissou,* N. Nebra, M. Fustier-Boutignon,* N. Mezailles*
    Angew. Chem. Int. Ed., 2017, 56, 12264-12267.

    ACIE 2017
    The first AuIII carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated AuIII precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the AuIII carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2), resulting in two types of C=C coupling reactions.

  • Rational Development of Catalytic Au(I)/Au(III) Arylation Involving Mild Oxidative Addition of Aryl Halides
    A. Zeineddine, L. Estévez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune,* D. Bourissou*
    Nature Comm. 2017, 8, 565.
    Natcom 2017
    The reluctance of gold to achieve oxidative addition reaction is considered as an intrinsic limitation for the development of gold-catalyzed cross-coupling reactions with simple and ubiquitous aryl halide electrophiles. Here, we report the rational construction of a Au(I)/Au(III) catalytic cycle involving a sequence of Csp2–X oxidative addition, Csp2–H auration and reductive elimination, allowing a gold-catalyzed direct arylation of arenes with aryl halides. Key to this discovery is the use of Me-Dalphos, a simple ancillary (P,N) ligand, that allows the bottleneck oxidative addition of aryl iodides and bromides to readily proceed under mild conditions. The hemilabile character of the amino group plays a crucial role in this transformation, as substantiated by density functional theory calculations.

  • Gold(III)​-​arene complexes by insertion of olefins into gold-​aryl bonds
    F. Rekhroukh, C. Blons, L. Estevez, S. Mallet-Ladeira, K. Miqueu,* A. Amgoune,* D. Bourissou*
    Chem. Sci. 2017, 8, 4539-4545.
    Chemsci 2017

    The synthesis and characterization of the first gold(III)–arene complexes are described. Well-defined (P,C)-cyclometalated gold(III)–aryl complexes were prepared and characterized by NMR spectroscopy. These complexes swiftly and cleanly reacted with norbornene and ethylene to provide cationic gold(III)–alkyl complexes, in which the remote phenyl ring was η2-coordinated to gold. The interaction between the aromatic ring and the gold(III) center was thoroughly analyzed by NMR spectroscopy, X-ray diffraction, and DFT calculations. The π–arene coordination was found to significantly influence the stability and reactivity of low coordinated gold(III) alkyl species.

  • β-Hydride Elimination at Low-Coordinate Gold(III) Centers
    F. Rekhroukh, L. Estevez, S. Mallet-Ladeira, K. Miqueu*, A. Amgoune*, D. Bourissou*
    J. Am. Chem. Soc., 2016, 138, 11920–11929.

    JACS 2016 beta-H

    This Article reports the first comprehensive study of β-hydride elimination at gold(III). The stability/fate of gold(III) alkyl species have been investigated experimentally and computationally. A series of well-defined cationic cyclometalated gold(III) alkyl complexes [(P,C)gold(III)(R)][NTf2] [(P,C) = 8-diisopropylphosphino-naphthyl; R = Me, nPr, nBu] have been synthesized and spectroscopically characterized. While the cationic gold(III) methyl derivative 3c is stable for days at room temperature, the gold(III) n-propyl and n-butyl complexes 3a,b readily undergo β-hydride elimination at low temperature to generate propylene and 2-butenes, respectively. The formation of internal olefins from the gold(III) n-butyl complex 3b shows that olefin isomerization takes place after β-hydride elimination. Computational studies indicate that this isomerization proceeds through a chain-walking mechanism involving a highly reactive gold(III) hydride intermediate and a sequence of β-hydride elimination/reinsertion into the Au–H bond. The reaction of the cationic gold(III) methyl complex 3c with ethylene was also explored. According to 1H and 13C NMR spectroscopy, a mixture of propylene, 1-butene, and 2-butenes is formed. DFT calculations provide detailed mechanistic insights and support the occurrence of migratory insertion of ethylene, β-hydride elimination, and olefin exchange at gold(III).

  • Experimental and Theoretical Evidence for an Agostic Interaction in a Gold(III) Complex
    F. Rekhroukh, L. Estévez, C. Bijani, K. Miqueu*, A. Amgoune*, D. Bourissou*
    Angew. Chem. Int. Ed. 2016, 55, 3414-3418.

    ACIE toc agostic

    The first agostic interaction in a gold complex is described. The presence of a bonding C−H⋅⋅⋅Au interaction in a cationic “tricoordinate” gold(III) complex was suggested by DFT calculations and was subsequently confirmed by NMR spectroscopy at low temperature. The agostic interaction was analyzed computationally using NBO and QTAIM analyses (NBO=natural bond orbital; QTAIM=quantum theory of atoms in molecules).

  • Reactivity of Gold Complexes towards Elementary Organometallic Reactions
    M. Joost, A. Amgoune*, D. Bourissou*
    Angew. Chem. Int. Ed. 2015, 54, 15022-15045.

    ACIE Revue Gold

    For a while, the reactivity of gold complexes was largely dominated by their Lewis acid behavior. In contrast to the other transition metals, the elementary steps of organometallic chemistry—oxidative addition, reductive elimination, transmetallation, migratory insertion—have scarcely been studied in the case of gold or even remained unprecedented until recently. However, within the last few years, the ability of gold complexes to undergo these fundamental reactions has been unambiguously demonstrated, and the reactivity of gold complexes was shown to extend well beyond π-activation. In this Review, the main achievements described in this area are presented in a historical context. Particular emphasis is set on mechanistic studies and structure determination of key intermediates. The electronic and structural parameters delineating the reactivity of gold complexes are discussed, as well as the remaining challenges.

  • Oxidative Addition of Carbon-Carbon Bonds to Gold
    M. Joost, L. Estevez, K. Miqueu,* A. Amgoune,* D. Bourissou*
    Angew. Chem. Int. Ed. 2015, 54, 5236-5240.

    Add Ox ACIE 2015

    The oxidative addition of strained C[BOND]C bonds (biphenylene, benzocyclobutenone) to DPCb (diphosphino-carborane) gold(I) complexes is reported. The resulting cationic organogold(III) complexes have been isolated and fully characterized. Experimental conditions can be adjusted to obtain selectively acyl gold(III) complexes resulting from oxidative addition of either the C(aryl)[BOND]C(O) or C(alkyl)[BOND]C(O) bond of benzocyclobutenone. DFT calculations provide mechanistic insight into this unprecedented transformation.

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    Cationic Gold(III) Alkyl Complexes: Generation, Trapping and Insertion of Norbornene.
    F. Rekhroukh, R. Brousses, A. Amgoune,* D. Bourissou.*
    Angew. Chem., Int. Ed. 2015, 54, 1266-1269.

    Coinage 1

    Migratory insertion of alkenes into gold–carbon bonds, a key, yet unprecedented organometallic reaction, is evidenced. Methide abstraction from a (P,C) cyclometallated gold(III) dimethyl complex with B(C6F5)3  is shown to generate a highly reactive cationic Au(III) complex. In the presence of norbornene, migratory insertion into the Au–C bond proceeds at low temperature. The resulting norbornyl complex was trapped with pyridines and chloride.

  • Enhanced π-Backdonation from Gold(I): Isolation of Original Carbonyl and Carbene Complexes.
    M. Joost, L. Estevez, S. Mallet-Ladeira, K. Miqueu,* A. Amgoune,* D. Bourissou*
    Angew. Chem., Int. Ed. 2014, 53, 14512-14516.

    Coinage 2

    Bending was shown to significantly enhance π-backdonation in gold(I) complexes. This strategy gives access to the first classical carbonyl complex of gold and allows the isolation of a diphenyl carbene complex that is stabilized by the gold fragment rather than the carbene substituents. The structures of these new complexes were thoroughly analyzed by spectroscopic, crystallographic, and computational means

  • Facile Oxidative Addition of Aryl-iodides to Gold(I) by Ligand Design: Bending Turns on Reactivity.
    M. Joost, A; Zeineddine, L. Estevez, S. Mallet-Ladeira, K. Miqueu, A. Amgoune,* D. Bourissou*
    J. Am. Chem. Soc. 2014, 136, 14654-14657.

    Coinage 3

    Thanks to rational ligand design, the first gold(I) complexes to undergo oxidative addition of aryl iodides were discovered. The reaction proceeds under mild conditions and is general. The ensuing aryl gold(III) complexes have been characterized by spectroscopic and crystallographic means. DFT calculations indicate that the bending induced by the diphosphine ligand plays a key role in this process.

  • Activation of Aryl Halides at Gold(I): Practical Synthesis of (P,C) Cyclometallated Gold(III) Complexes.
    J. Guenther, S. Mallet-Ladeira, L. Estevez, K. Miqueu, A. Amgoune,* D. Bourissou,*
    J. Am. Chem. Soc. 2014, 136, 1778-1781

    Coinage 5

    Taking advantage of phosphine chelation, direct evidence for oxidative addition of Csp2−X bonds (X= I, Br) to a single gold atom is reported. NMR studies and DFT calculations provide insight into this unprecedented transformation, which gives straightforward access to stable (P,C) cyclometalated gold(III) complexes.

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