Personne :
Boudreau, Josée

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Boudreau
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Josée
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Département de chimie, Faculté des sciences et génie, Université Laval
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ncf11861306
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Voici les éléments 1 - 8 sur 8
  • Publication
    Accès libre
    Coordination of ethylene to a zwitterionic Rh(III) half-sandwich complex : influence of ambiphilic Ligands on reactivity
    (ACS, 2011-01-18) Boudreau, Josée; Fontaine, Frédéric-Georges
    The reactivity of Rh(III) half-sandwich complex Cp*RhMe2(κP-μAl-MePMe2CH2AlMe2) 2 (Cp* = η5-pentamethylcyclopentadienyl) with ethylene was investigated. Coordination of ethylene (or ethylene-d4) gave a mixture of products including as principal species zwitterionic complexes Cp*Rh+Me(C2H4)(PMe2CH2AlMe3−) 4 (or 4-d4) and [Cp*Rh+Me(C2H4)(PMe2CH2AlMe3−)][AlMe3] (4′), after the abstraction of a Rh-methyl group by the pendant Lewis acid, and Cp*RhMe2(PMe2CH2AlMe2·C2H4) (5). Heating this reaction mixture at 50 °C results in the generation of propene (or propene-d3,4), methane (or methane-d1), and trace amounts of butene, as organic materials, as well as previously characterized [Cp*RhMe(μ2-η2(P,C)-PMe2CH2)]2 (10) and rhodium(I) species. Two different pathways for the reactivity of the zwitterionic π-complex were investigated by density functional theory (DFT). It is likely that propene is formed by β-hydride elimination from a cationic Rh-propyl fragment that is generated either by insertion of ethylene into a Rh−C bond or by a nucleophilic attack of the methyl-aluminate fragment on coordinated ethylene. After release of propene, the neutral complex Cp*RhHMe(PMe2CH2AlMe2) 11 is most likely responsible for the reductive elimination of methane.
  • Publication
    Accès libre
    Synthèse et réactivité d'un complexe de rhodium(iii) possédant un ligand ambiphile phosphine-alane
    (2011) Boudreau, Josée; Fontaine, Frédéric-Georges
    Cet ouvrage démontre le potentiel qu'ont les ligands ambiphiles pour des applications dans des systèmes d'intérêt en activation du lien C-H d'alcanes. La synthèse du complexe Cp*RhMe2(PMe2CH2AlMe2) (Cp* = r*5-C5Me5) est présentée et l'étude de sa réactivité démontre que l'incorporation d'un fragment acide de Lewis dans la sphère de coordination secondaire de l'atome de rhodium influence significativement la réactivité au niveau de ce métal de transition. Celle-ci est enrichie par la capacité du fragment acide de Lewis d'abstraire un ligand méthylé pour former le zwitterion transitoire Cp*Rh+Me(PMe2CH2ArMe3). Il a été démontré par l'expérience et par la modélisation numérique que diverses bases de Lewis peuvent se lier à l'atome d'aluminium du complexe neutre ou au métal de transition du complexe zwitterionique, et que l'équilibre entre ces modes de coordination est dicté en partie par la « dureté » de la base de Lewis. L'influence du ligand ambiphile s'est aussi manifestée lors de l'étude de la réactivité du même complexe avec différents substrats insaturés tels que l'éthylène, les alcynes terminaux et le dioxyde de carbone. La réversibilité du processus d'ionisation s'est avéré un paramètre clé de la réaction avec l'éthylène, car suite à la formation du zwitterion Cp*Rh+H(PMe2CH2Al"Me3) le retour à l'espèce neutre Cp*RhHMe(PMe2CH2AlMe2) permet d'accéder par élimination réductrice du méthane à un intermédiaire hautement réactif de Rh(I) analogue des composés de type Cp*M(PMe3) (M = Rh, lr) capables d'addition oxydante du lien C-H d'alcanes mais typiquement générés par voie photochimique. Différents facteurs semblent faire en sorte qu'aucune addition oxydante à partir de cet intermédiaire n'a pu être observée, notamment la formation d'une interaction Rh—*»A1 qui semble stabiliser le complexe réduit. Certains paramètres qui pourraient améliorer ces résultats sont discutés. Les composés ambiphiles (PR2CH2AlMe2)2 (R = Me, Ph) interagissent en solution ou à l'état solide avec le CO2 pour former un type d'adduit préalablement formé strictement avec des « Frustrated Lewis Pairs », pourtant les composés ambiphiles présentés sont des dimères stables. L'étude de ces adduits a mené à la formation de carboxylates d'aluminium et à l'observation d'un mode d'activation inédit pour le CO2.
  • Publication
    Accès libre
    Coordination to a di-tert-butylphosphidoboratabenzene ligand with electronically unsaturated group 10 transition metals
    (American Chemical Society, 2012-08-22) Boudreau, Josée; Fontaine, Frédéric-Georges; Maron, Laurent; Macha, Bret; Maris, Thierry
    A new boratabenzene-phosphine ligand, di-tert-butylphosphidoboratabenzene, [DTBB]−, has successfully been synthesized by reduction of the corresponding di-tert-butylchlorophosphidoborabenzene compound (2). The species was structurally characterized with both K+ (3) and 18-crown-6·K+ (4) as counterions. Reactions of two equivalents of di-tert-butylphosphidoboratabenzene with NiBr2(PPh3)2, PtCl2, and PtCl2(COD) were undertaken and were successful in yielding three new organometallic boratabenzene species, (μ-κ-η6-C5H5BP(tBu)2)2Ni2 (5), (η3-(C,B,P)-C5H5BP(tBu)2)2Pt (6), and (η3-(C,B,P)-C5H5BP(tBu)2)(κ-C8H12(P(tBu)2BC5H5)Pt (7), respectively. The di-tert-butylphosphidoboratabenzene species displays a remarkable tendency to coordinate to transition metal species in two distinct modes closely associated with other reported boratabenzene and allyl-like interactions. Also of interest is the ability for di-tert-butylphosphidoboratabenzene to be able to coordinate within monomeric as well as dimeric transition metal compounds. The synthesis and characterization will be discussed in detail along with DFT calculations in order to validate these research findings.
  • Publication
    Accès libre
    Coordination chemistry of neutral (Ln)–Z amphoteric and ambiphilic ligands
    (Wiley, 2008-10-27) Boudreau, Josée; Fontaine, Frédéric-Georges; Thibault, Marie-Hélène
    This review focuses on the coordination chemistry of neutral ambiphilic and amphoteric ligands. The various designs of molecules having both donor and acceptor moieties and the strategies to prevent self‐aggregation and favour transition‐metal coordination will be discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
  • Publication
    Accès libre
    MS-TOF study of the formation of thiolato bridged rhodium oligomers
    (Wiley, 2010-04-08) Boudreau, Josée; Grenier-Desbiens, Jérôme; Fontaine, Frédéric-Georges
    The complex [Cp*Rh(μ‐SPh)3RhCp*]Cl was used as a starting material to synthesize various oligomeric materials of the general formula [Cp*Rh(μ‐SPh)x(μ‐Cl)3–x{Rh(μ‐SPh)3}nRhCp*] (x = 1 to 3; n = 1 to 4), which are formally formed by insertion of nRh(SPh)3 units into one μ‐Rh–SPh bond. The insertion of Ir(SPh)3 was also observed to generate theheterotrimetallic species. All complexes were observed by using HRMS‐TOF and [Cp*Rh(μ‐SPh)3Rh(μ‐SPh)3RhCp*]Cl, [3+]Cl, was characterized by using X‐ray crystallography.
  • Publication
    Accès libre
    Ambiphilic molecules for trapping reactive intermediates : interrupted Nazarov reaction of allenyl vinyl ketones with Me2PCH2AlMe2
    (RCS, 2012-09-28) Boudreau, Josée; Fontaine, Frédéric-Georges; Marx, Vanessa M.; Courtemanche, Marc-André; Burnell, Jean
    The addition of the ambiphilic molecule Me2AlCH2PMe2 (1) to the allenyl vinyl ketone 2 gave a trapped Nazarov reaction product. Under kinetic control, the addition of the phosphine was on the methylated carbon, contrary to expected steric and electronic considerations. Computational data pointed to hydrogen bonding between the phosphine and the methyl group guiding the regiochemistry of this reaction. This product rearranged to provide the expected, regioisomeric Nazarov product. With additional 1 this compound yielded a Michael-addition product via a retro-Nazarov process
  • Publication
    Accès libre
    Reactivity of Lewis pairs (R2PCH2AlMe2)2 with carbon dioxide
    (2011-09-07) Boudreau, Josée; Fontaine, Frédéric-Georges; Courtemanche, Marc-André
    Species R2PCH2AlMe2 (R = Me, Ph) are stable Lewis adducts but still react with CO2 both in solution and in the solid state. The CO2 adducts undergo a rearrangement unprecedented for ambiphilic molecules to form aluminium carboxylates. A new spirocyclic compound was also obtained by double Lewis pair activation of CO2.
  • Publication
    Accès libre
    Coordination of a bifunctional ligand to a rhodium(III) dimethyl complex : Lewis acidity enhancement by chelation
    (American Chemical Society, 2007-06-12) Boudreau, Josée; Mathiotte, Sophie; Drouin, Frédéric; Fontaine, Frédéric-Georges; Michaud, Annie; Thibault, Marie-Hélène; Sigouin, Olivier
    The addition of the ambiphilic compound (Me2PCH2AlMe2)2 (1) to Cp*RhMe2(DMSO) (DMSO = dimethylsulfoxide) (2) gives Cp*RhMe2(PMe2CH2AlMe2·DMSO) (3·DMSO). The addition of Lewis acids (LA) such as La(dbm)3 (dbm = dibenzoylmethane) and AlMe3 to a solution of complex 3·DMSO gives a competition reaction that results in the formation of LA·DMSO and Cp*RhMe2(PMe2CH2AlMe2) (3). When heated to 40 °C, complex 3 ionizes to a putative zwitterionic species, Cp*Rh+Me(PMe2CH2AlMe3-) (3‘), which is converted to [Cp*Rh(Me)(μ2-η2-Me2PCH2)]2 (4) irreversibly. Spin saturation transfer experiments demonstrated that the rate of the methyl abstraction by the alane moiety was 0.76 ± 0.09 s-1, while the rate of abstraction of the methyl in Cp*RhMe2(PMe3) by AlMe3 was 0.10 ± 0.02 s-1. The zwitterionic species 3‘ could be trapped in solution by addition of PMe3 to afford both Cp*Rh+Me(PMe3)(Me2PCH2AlMe3-) (5) and [Cp*Rh+Me(PMe3)(Me2PCH2AlMe2)]AlMe4- (6). When compound 1 was added to complex 3‘, the formation of the zwitterionic complex Cp*Rh+Me(η2-Me2PCH2Al-Me2CH2PMe2) (7) was observed.