20 research outputs found
SynthÚse et réactivité de complexes à ligand iminophosphorane : des métaux de transition aux actinides
For the past decades, organometallic and coordination chemistry have proven to be fields of major importanceby allowing the preparation of catalysts that are able to perform unpreceded chemical reactions, in addition with the discovery of unusual species with physical and chemical properties that are very interesting. All these studies are underlining the primordial role of the ligand, which allows fine-tuning of the properties of such species. Our laboratory has gained considerable experience in the synthesis and the study of the coordination chemistry of ligands bearing the iminophosphorane moieties (RN=PRâ3). These ligands, still poorly studied in the literature, present electronic properties that are strongly deviating from those of their carbon-analogues, i.e. imines. This thesis is focused on the synthesis of a new family of (un)symmetrical, lutidine-based iminophosphorane ligands. Initially, the coordination chemistry of these ligands with transition metals is described with a focus on copper. Hemilabile behaviour is highlighted and shown to be related to the oxidation state of the copper metal centre, furnishing a redox-switchable system. These complexes are then shown to be useful in a number of catalytic reactions. Then, the coordination chemistry of these ligands is explored with lanthanides, more particularly divalent. These metals are strong reductants and are able to activate a variety of substrates like carbon dioxide for example, however such reactivities must be restrained by an appropriate ligand set. In particular, the study of the coordination chemistry of the new ligand family with metallocenes of ytterbium(II) is exhibiting lability phenomena, either of the iminophosphorane ligand or of the phospholyl ligand on the ytterbium centre. Moreover, the coordination chemistry of these ligands with uranium is briefly described. The synthesis and the coordination chemistry of mixed iminophosphorane-phosphine ligands are described subsequently. These ligands exhibit properties of dearomatization of the central pyridine scaffold. This phenomenon is studied with palladium(II) complexes, as the reactivity of these species with boranes. The reactivity of these new mixed ligands is also studied with ruthenium. Particularly, the presence of a hydride leads to the formation of an organometallic bond between the ligand and the ruthenium centre with the loss of hydrogen. In the last part, a new family of ligands bearing phenoxide moieties is studied. The oxidative and reductive chemistry of the copper and uranium complexes are explored and show a large divergence in comparison with the imines analogues of these ligands. Finally, the use of their nickel complexes as catalysts for the dimerization of ethylene is presented. All the results are supported by solid-state analysis, mainly by X-ray diffraction experiments; in solution the behavior of the species are studied by means of multinuclear NMR studies; finally some compounds are also investigated in silico by DFT calculations.La chimie organomĂ©tallique et de coordination a prouvĂ© dans les derniĂšres dĂ©cennies son importance enpermettant lâobtention de catalyseurs capables dâeffectuer des rĂ©actions chimiques sans prĂ©cĂšdent mais permettant aussi la dĂ©couverte dâespĂšces prĂ©sentant des propriĂ©tĂ©s physiques et chimiques trĂšs intĂ©ressantes. Il ressort de ces Ă©tudes que les ligands jouent un rĂŽle primordial en modulant finement les propriĂ©tĂ©s de telles espĂšces. Notre laboratoire a acquis une grande expĂ©rience dans la synthĂšse et lâĂ©tude de la chimie de coordination de ligands prĂ©sentant la fonctionnalitĂ© iminophosphorane (RN=PRâ3). Ces ligands, encore peu Ă©tudiĂ©s dans la littĂ©rature, prĂ©sentent des propriĂ©tĂ©s Ă©lectroniques divergeant fortement de leurs analogues carbonĂ©s, les imines. Ce travail de doctorat est centrĂ© sur la synthĂšse dâune nouvelle famille de ligands iminophosphoranes symĂ©triques ou non, comportant le motif de lutidine. Dans un premier temps, la chimie de coordination de ces espĂšces avec les mĂ©taux de transition et, plus particuliĂšrement, avec le cuivre est dĂ©crite. Des phĂ©nomĂšnes dâhĂ©milabilitĂ© du ligand, liĂ©s Ă lâĂ©tat dâoxydation du mĂ©tal, sont mis en Ă©vidence , fournissant ainsi un systĂšme commutable par un stimulus redox. Ces espĂšces sont aussi employĂ©es dans le cadre de quelques rĂ©actions catalytiques. La chimie de ces nouveaux ligands symĂ©triques est ensuite explorĂ©e avec les lanthanides, plus particuliĂšrement divalents. Ces mĂ©taux fortement rĂ©ducteurs sont capables dâactiver de nombreux substrats comme le dioxyde de carbone, mais leurs rĂ©activitĂ©s doivent ĂȘtre souvent canalisĂ©es par des ligands appropriĂ©s. LâĂ©tude de la chimie de coordination de la nouvelle famille de ligands iminophosphoranes avec les mĂ©tallocĂšnes dâytterbium(II) permet de mettre en Ă©vidence des phĂ©nomĂšnes de labilitĂ©, soit du ligand iminophosphorane, soit des ligands phospholes de lâytterbium. LâĂ©tude de la chimie de coordination de ces espĂšces avec lâuranium est enfin briĂšvement abordĂ©e. Par la suite, la synthĂšse et la chimie de coordination de ligands mixtes iminophosphoranes-phosphines sont abordĂ©es. Ces ligands prĂ©sentent des propriĂ©tĂ©s de dĂ©aromatisation de la pyridine centrale. La chimie de coordination et lâĂ©tude du phĂ©nomĂšne de dĂ©aromatisation avec le palladium(II) sont prĂ©sentĂ©s, ainsi que la rĂ©activitĂ© de ces espĂšces vis-Ă -vis des boranes. La rĂ©activitĂ© de ces nouveaux ligands vis-Ă -vis du ruthĂ©nium est aussi explorĂ©e. En particulier la prĂ©sence dâun hydrure conduit Ă la formation dâune liaison organomĂ©tallique entre le ligand et le ruthĂ©nium et le dĂ©part de dihydrogĂšne. Dans une derniĂšre partie, des ligands iminophosphoranes prĂ©sentant une fonctionnalitĂ© phĂ©nolate sont Ă©tudiĂ©s. La chimie dâoxydation et de rĂ©duction des complexes de cuivre et dâuranium est explorĂ©e et met en Ă©vidence une forte divergence par rapport aux analogues imines de ces ligands. Enfin, lâutilisation de complexes de nickel(II) pour catalyse de dimĂ©risation de lâĂ©thylĂšne est dĂ©crite. Lâensemble des rĂ©sultats est soutenu par des analyses Ă lâĂ©tat solide, principalement par diffraction des rayons X ; en solution, par des Ă©tudes RMN multinoyaux mais aussi in silico par des calculs DFT
Complexation and Redox Chemistry of Neptunium, Plutonium and Americium with a Hydroxylaminato Ligand
Versatile coordination chemistry of a bis(methyliminophosphoranyl)pyridine ligand on copper centres
International audienc
Palladium( ii ) complexes featuring a mixed phosphineâpyridineâiminophosphorane pincer ligand: synthesis and reactivity
International audienc
η 5 âη 1 Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR 1 J YbâP Coupling Constants
International audienc
Fe II complexes supported by an iminophosphorane ligand: synthesis and reactivity
International audienceFe II complexes incorporating mixed phosphineâiminophosphorane ligands have rarely been investigated; synthesis and reactivity studies of phosphineâlutidineâiminophosphorane iron complexes are reported
η<sup>5</sup>âη<sup>1</sup> Switch in Divalent Phosphaytterbocene Complexes with Neutral Iminophosphoranyl Pincer Ligands: Solid-State Structures and Solution NMR <sup>1</sup><i>J</i><sub>YbâP</sub> Coupling Constants
This
paper reports the synthesis of a series of complexes based
on the bisÂ(pentamethylcyclopentadienyl)ÂytterbiumÂ(II) (<b>1</b>; Cp*<sub>2</sub>Yb) and bisÂ(tetramethylphospholyl)ÂytterbiumÂ(II)
(<b>2</b>; Tmp<sub>2</sub>Yb) fragments bearing an additional
neutral bisÂ(methyliminophosphoranyl)Âpyridine ligand (<b>L</b>) on which the steric demand is modulated at the phosphorus position
(triethyl, <b>L</b><sup><b>Et</b></sup>; triphenyl, <b>L</b><sup><b>Ph</b></sup>; tricyclohexyl, <b>L</b><sup><b>Cy</b></sup>) to yield the original complexes Cp*<sub>2</sub>Yb<b>L</b><sup><b>Et</b></sup> (<b>1-L</b><sup><b>Et</b></sup>), Cp*<sub>2</sub>Yb<b>L</b><sup><b>Ph</b></sup> (<b>1-L</b><sup><b>Ph</b></sup>), Tmp<sub>2</sub>Yb<b>L</b><sup><b>Et</b></sup> (<b>2-L</b><sup><b>Et</b></sup>), Tmp<sub>2</sub>Yb<b>L</b><sup><b>Ph</b></sup> (<b>2-L</b><sup><b>Ph</b></sup>), and Tmp<sub>2</sub>Yb<b>L</b><sup><b>Cy</b></sup> (<b>2-L</b><sup><b>Cy</b></sup>), while no reaction occurs between <b>1</b> and <b>L</b><sup><b>Cy</b></sup>. The crystal
structures of these sterically crowded complexes are reported as well
as room-temperature NMR data for all the complexes. The solid-state
coordination mode of <b>L</b><sup><b>R</b></sup> differs
depending on the nature of the fragments <b>1</b> and <b>2</b> and on the steric bulk of <b>L</b><sup><b>R</b></sup>. The crystal structure of the divalent Tmp<sub>2</sub>YbÂ(py)<sub>2</sub> (<b>3</b>) is also reported for structural and spectroscopic
comparisons. Interestingly, in both <b>2-L</b><sup><b>Et</b></sup> and <b>2-L</b><sup><b>Cy</b></sup>, one of the
two Tmp ligands coordinates in an η<sup>1</sup> rather than
in an η<sup>5</sup> fashion, a relevant coordination mode for
the study of sterically induced reductions. The behavior of those
complexes in solution varies with the sterics and electronics of the
ligands, as demonstrated by variable-temperature NMR experiments.
In solution, the <sup>1</sup><i>J</i><sub>YbâP</sub> coupling is used to track the coordination mode of the Tmp ligand
and a large difference in the <sup>1</sup><i>J</i><sub>YbâP</sub> coupling constant allows the distinction between an η<sup>5</sup> coordination mode and a dynamic η<sup>5</sup>âη<sup>1</sup> switch
Nickel Complexes Featuring IminophosphoraneâPhenoxide Ligands for Catalytic Ethylene Dimerization
International audienc
Synthesis and Reactivity of Low-Valent f-Element Iodide Complexes with Neutral Iminophosphorane Ligands
International audienc