70 research outputs found
Etudes Théoriques de Nouvelles Réactions Organométalliques : de la Catalyse à l'Or à la Chimie des Lanthanides Divalents
This dissertation comprises a series of theoretical studies of organometallic and organolanthanidiques complexes.Mon travail de thĂšse est constituĂ© dâun ensemble dâĂ©tudes thĂ©oriques portant sur des complexes organomĂ©talliques et organolanthanidiques. Ces Ă©tudes ont toutes Ă©tĂ© rĂ©alisĂ©es en Ă©troite collaboration avec des expĂ©rimentateurs au sein du laboratoire. Une de ces Ă©tudes concerne la rĂ©action de silylation dĂ©shydrogĂ©nante des alcools catalysĂ©e par des complexes cationiques dâor (I) possĂ©dant un ligand bidente dĂ©rivĂ© du Xantphos, le XDPP. Les rĂ©sultats de cette Ă©tude nous ont conduits Ă proposer un cycle catalytique passant par une premiĂšre Ă©tape de transfert dâhydrure du silane vers lâor et faisant intervenir le contre anion de façon explicite. Une telle participation du contre anion nâest pas courante dans la littĂ©rature et permet de rationaliser lâinfluence de celui-ci sur la cinĂ©tique de la rĂ©action observĂ©e expĂ©rimentalement. Un autre pan important de ma thĂšse porte sur la rĂ©activitĂ© de complexes divalents de lanthanides. La question centrale de ces travaux est celle de lâinfluence des propriĂ©tĂ©s Ă©lectroniques des ligands sur les propriĂ©tĂ©s redox de ces complexes. En effet, il est gĂ©nĂ©ralement admis que les lanthanides conduisent Ă des complexes de coordination dans lesquels la liaison mĂ©tal-ligand peut ĂȘtre considĂ©rĂ©e comme ionique (consĂ©quence de la contraction spatiale des orbitales 4f). Or, des expĂ©riences rĂ©centes font soupçonner lâexistence dâune influence non seulement stĂ©rique mais Ă©galement Ă©lectronique des ligands sur la rĂ©activitĂ© des complexes rĂ©sultants. Nos rĂ©sultats viennent Ă©tayer cette hypothĂšse et apportent de nouveaux Ă©lĂ©ments de discussion quant Ă la nature exacte de lâinteraction mĂ©tal-ligand dans ces complexes organolanthanidiques
Redox-active phosphines: synthesis and crystal structures of palladium(II) complexes of a metallaphosphine in two different oxidation states.
International audienceThe redox-active metallaphosphine [Fe(dppe)(η(5)-C5Me5)(CâĄC-PPh2)] reacts with [Pd(1,5-cod)Cl2] to give mono- and bis-phosphine coordinated palladium centres as a function of stoichiometry, and these complexes provide a stable redox-active platform which allows reversible one-electron {Fe(II)âFe(III)(+)} oxidations within the palladium coordination sphere
Synthesis of Functionalised 3-Isochromanones by Silylcarbocyclisation/Desilylation Reactions
A new protocol for the synthesis of 3-isochromanone derivatives based on rhodium-promoted silylcarbocyclisation
reactions of ethynylbenzyl alcohol with different arylsilanes is described. The structure of the isochromanone depends upon the reaction conditions used: when the reaction is carried out without base, (Z)-4-(aryldimethylsilyl)methylene]isochroman-3-ones are obtained as major products. These compounds can be submitted to a desilylation/aryl migration reaction to give 4-(arylmethyl)isochroman-3-ones in high yields. In contrast, in the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), hydrogenation of methyleneisochroman-3-ones takes place, and the corresponding -(silylmethyl)-3-isochromanones are formed. Moreover, when internal alkynes are treated with hydrosilanes under silylcarbocyclisation reaction conditions, alcoholysis of the hydrosilanes occurs exclusively
Theoretical Insights into the Nature of Divalent Lanthanide-Ligand Interactions
International audienceThe nature of the metal-ligand interaction in divalent samarium complexes is investigated by a variety of quantum chemical tools and compared to the analogous strontium-ligand interaction. The complexes under study are the decamethylsamarocene Sm(C5Me5)(2) the octamethyldiphosphasamarocene Sm(C4Me4P)(2), and the decamethylstrontocene Sr(C5Me5)(2). Molecular orbital descriptions, binding energy decompositions and topological analyses based on the electron density reveal the non-negligible role of covalency in the samarium-ligand interaction. The results are supported by an orbital energetic contribution in the metal-ligand interaction and a number of samarium-carbon bond critical points and electron localization function valence basins. The covalent contribution to the samarium-ligand bond contrasts with the highly ionic strontium-ligand interaction
Mechanism of the Dehydrogenative Silylation of Alcohols Catalyzed by Cationic Gold Complexes : an Experimental and Theoretical Study (affiche)
Theoretical Treatment of Redox Processes Involving Lanthanide(II) Compounds: Reactivity of Organosamarium(II) and Organothulium(II) Complexes with CO2 and Pyridine
International audienc
Mécanisme de la Réaction de Silylation Déhydrogénative des Alcools en présence de Complexes d'Or : Etude Expérimentale et Théorique (affiche)
Mechanism of the Dehydrogenative Silylation of Alcohols Catalyzed by Cationic Gold Complexes: An Experimental and Theoretical Study
International audienc
Redox-induced reversible P-P bond formation to generate an organometallic Ï4λ4-1,2-biphosphane dication.
International audienc
Exploring isofunctional molecules: design of a benchmark and evaluation of prediction performance
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