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Robe H Morris - One of the best experts on this subject based on the ideXlab platform.

  • exploiting metal ligand bifunctional reactions in the design of iron asymmetric hydrogenation catalysts
    Accounts of Chemical Research, 2015
    Co-Authors: Robe H Morris
    Abstract:

    ConspectusThis is an Account of our development of iron-based catalysts for the asymmetric transfer hydrogenation (ATH) and asymmetric pressure hydrogenation (AH) of ketones and imines. These chemical processes provide enantiopure alcohols and amines for use in the pharmaceutical, agrochemical, fragrance, and other fine chemical industries. Fundamental principles of bifunctional reactivity obtained by studies of ruthenium catalysts by Noyori’s group and our own with tetradentate ligands with tertiary phosphine and secondary amine donor groups were applied to improve the performance of these first iron(II) catalysts. In particular the correct positioning of a bifunctional H–Fe–NH unit in an iron hydride amine complex leads to exceptional catalyst activity because of the low energy barrier of dihydrogen transfer to the Polar Bond of the substrate. In addition the ligand structure with this NH group along with an asymmetric array of aryl groups orients the incoming substrate by hydrogen-Bonding, and steric i...

Brunel Paul - One of the best experts on this subject based on the ideXlab platform.

  • Pincer complexes and metal/ligand cooperativity : application in catalysis
    2018
    Co-Authors: Brunel Paul
    Abstract:

    Ce travail de thèse porte sur la chimie organométallique des complexes pince indényle/indénediide de palladium et de platine et leurs applications en catalyse coopérative métal-ligand. Le premier chapitre de ce manuscrit fait un point bibliographique non-exhaustif du domaine de la coopérativité métal-ligand, des travaux de Noyori sur l'hydrogénation asymétrique, jusqu'aux récents travaux de Milstein avec les ligands désaromatisés. Les ligands pince sont également présentés. Du premier exemple PCP décrit par Shaw jusqu'au CNC développé par Bezuidenhout. La versatilité de ces ligands est illustrée à travers quelques modifications permettant des réactivités originales ou l'isolation d'espèces hautement instables. Le second chapitre présente une nouvelle réaction de formation de cycle avec le complexe pince indénediide de palladium. Cette réaction implique pour la première fois deux molécules de substrat, le CO2 comme source C1 et les propargylamines/homopropargylamines. L'étude mécanistique du système a permis d'établir l'implication de la coopérativité métal-ligand. Ensuite, le troisième chapitre est un chapitre de chimie exploratoire. De nouvelles réactivités ont été étudiées avec les complexes pince de platine. L'activation de liaisons peu polaires telles que H-H et H-Si ont permis la réduction de liaisons insaturées. Les propositions mécanistiques, qu'il reste à confirmer, semblent indiquer que les métathèses ?, ainsi que les insertions migratoires, sont possibles avec ces complexes. Finalement, le dernier chapitre est consacré au développement d'un nouveau ligand pince ayant la particularité d'être hémilabile et ouvrant ainsi la voie à de nouvelles réactivités. Sa coordination au palladium, ainsi que la déprotonation de ce dernier, a permis le développement d'un complexe coopératif qui a été testé en cycloisomérisation. L'ensemble de ces travaux reflètent l'importance des ligands pince indényle/indénediide et de la coopérativité métal-ligand en catalyse.This Ph.D. work deals with organometallic chemistry of indenyl/indenediide palladium and platinum pincer complexes and their applications in metal-ligand cooperative catalysis. The first chapter of this manuscript compiled a non-exhaustive bibliographic survey of the field of metal-ligand cooperation, from Noyori's system applied to the asymmetric hydrogenation, to the recent examples described by Milstein involving non-aromatic pincer ligands. Pincer ligands are also presented. Starting from the first example, in which Shaw shed light a PCP pincer, to the contemporary CNC pincer reported by Bezuidenhout. The versatility of those ligands is illustrated through few modulations allowing originals reactivities or stabilisation of highly unstable species. The second chapter is focused on the development of a new catalytic reaction with the indenediide palladium pincer complex. This reaction entail, for the first time, two substrates, the CO2 as a C1 source and propargylamines/homopropargylamines. The mechanistic studies turn out the importance of the metal-ligand cooperativity. Then, the third chapter concerns exploratory chemistry. New reactivities have been studied with the platinum complexes. The activation of low Polar Bond such as H-H and H-Si allowed the reduction of unsatured C-C Bond. The mechanistic propositions, that remain to be confirmed, seem to indicate the feasibility of ? Bond metathesis and migratory insertions. Finally, the last chapter is dedicated to the development of a new ligand. The latter showed the distinctive characteristic to be hemilabile, leading the way of new reactivities. His coordination to palladium, followed by his deprotonation to give rise to the non-innocent nature of the complex is presented, as well as the application of the resulting complex in the context of a cycloisomerisation. Those results are reflecting the importance of the indenyl and indenediide pincer ligands besides the metal-ligand cooperativity in catalysis

  • Complexes pince et cooperativité métal/ligand : application en catalyse
    HAL CCSD, 2018
    Co-Authors: Brunel Paul
    Abstract:

    This Ph.D. work deals with organometallic chemistry of indenyl/indenediide palladium and platinum pincer complexes and their applications in metal-ligand cooperative catalysis. The first chapter of this manuscript compiled a non-exhaustive bibliographic survey of the field of metal-ligand cooperation, from Noyori's system applied to the asymmetric hydrogenation, to the recent examples described by Milstein involving non-aromatic pincer ligands. Pincer ligands are also presented. Starting from the first example, in which Shaw shed light a PCP pincer, to the contemporary CNC pincer reported by Bezuidenhout. The versatility of those ligands is illustrated through few modulations allowing originals reactivities or stabilisation of highly unstable species. The second chapter is focused on the development of a new catalytic reaction with the indenediide palladium pincer complex. This reaction entail, for the first time, two substrates, the CO2 as a C1 source and propargylamines/homopropargylamines. The mechanistic studies turn out the importance of the metal-ligand cooperativity. Then, the third chapter concerns exploratory chemistry. New reactivities have been studied with the platinum complexes. The activation of low Polar Bond such as H-H and H-Si allowed the reduction of unsatured C-C Bond. The mechanistic propositions, that remain to be confirmed, seem to indicate the feasibility of ? Bond metathesis and migratory insertions. Finally, the last chapter is dedicated to the development of a new ligand. The latter showed the distinctive characteristic to be hemilabile, leading the way of new reactivities. His coordination to palladium, followed by his deprotonation to give rise to the non-innocent nature of the complex is presented, as well as the application of the resulting complex in the context of a cycloisomerisation. Those results are reflecting the importance of the indenyl and indenediide pincer ligands besides the metal-ligand cooperativity in catalysis.Ce travail de thèse porte sur la chimie organométallique des complexes pince indényle/indénediide de palladium et de platine et leurs applications en catalyse coopérative métal-ligand. Le premier chapitre de ce manuscrit fait un point bibliographique non-exhaustif du domaine de la coopérativité métal-ligand, des travaux de Noyori sur l'hydrogénation asymétrique, jusqu'aux récents travaux de Milstein avec les ligands désaromatisés. Les ligands pince sont également présentés. Du premier exemple PCP décrit par Shaw jusqu'au CNC développé par Bezuidenhout. La versatilité de ces ligands est illustrée à travers quelques modifications permettant des réactivités originales ou l'isolation d'espèces hautement instables. Le second chapitre présente une nouvelle réaction de formation de cycle avec le complexe pince indénediide de palladium. Cette réaction implique pour la première fois deux molécules de substrat, le CO2 comme source C1 et les propargylamines/homopropargylamines. L'étude mécanistique du système a permis d'établir l'implication de la coopérativité métal-ligand. Ensuite, le troisième chapitre est un chapitre de chimie exploratoire. De nouvelles réactivités ont été étudiées avec les complexes pince de platine. L'activation de liaisons peu polaires telles que H-H et H-Si ont permis la réduction de liaisons insaturées. Les propositions mécanistiques, qu'il reste à confirmer, semblent indiquer que les métathèses ?, ainsi que les insertions migratoires, sont possibles avec ces complexes. Finalement, le dernier chapitre est consacré au développement d'un nouveau ligand pince ayant la particularité d'être hémilabile et ouvrant ainsi la voie à de nouvelles réactivités. Sa coordination au palladium, ainsi que la déprotonation de ce dernier, a permis le développement d'un complexe coopératif qui a été testé en cycloisomérisation. L'ensemble de ces travaux reflètent l'importance des ligands pince indényle/indénediide et de la coopérativité métal-ligand en catalyse

Kröger J. - One of the best experts on this subject based on the ideXlab platform.

  • Electric-field control of a single-atom Polar Bond
    'American Physical Society (APS)', 2021
    Co-Authors: Omidian M., Leitherer S., Neel N., Brandbyge M., Kröger J.
    Abstract:

    The Polar covalent Bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) is exposed to an external electric field. For one field orientation the Au-C Bond is strong enough to sustain the mechanical load of partially detached graphene, whilst for the opposite orientation the Bond breaks easily. Calculations based on density functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling Bond forces that reflect the Polar character of the Bond. Field-induced charge transfer between the atomic orbitals modifies the Polarity of the different electronegative reaction partners and the Au-C Bond strength

Omidian M. - One of the best experts on this subject based on the ideXlab platform.

  • Electric-field control of a single-atom Polar Bond
    'American Physical Society (APS)', 2021
    Co-Authors: Omidian M., Leitherer S., Neel N., Brandbyge M., Kröger J.
    Abstract:

    The Polar covalent Bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) is exposed to an external electric field. For one field orientation the Au-C Bond is strong enough to sustain the mechanical load of partially detached graphene, whilst for the opposite orientation the Bond breaks easily. Calculations based on density functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling Bond forces that reflect the Polar character of the Bond. Field-induced charge transfer between the atomic orbitals modifies the Polarity of the different electronegative reaction partners and the Au-C Bond strength

Neel N. - One of the best experts on this subject based on the ideXlab platform.

  • Electric-field control of a single-atom Polar Bond
    'American Physical Society (APS)', 2021
    Co-Authors: Omidian M., Leitherer S., Neel N., Brandbyge M., Kröger J.
    Abstract:

    The Polar covalent Bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) is exposed to an external electric field. For one field orientation the Au-C Bond is strong enough to sustain the mechanical load of partially detached graphene, whilst for the opposite orientation the Bond breaks easily. Calculations based on density functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling Bond forces that reflect the Polar character of the Bond. Field-induced charge transfer between the atomic orbitals modifies the Polarity of the different electronegative reaction partners and the Au-C Bond strength