Dianions géminés stabilisés pour la formation de liaisons multiples carbone - terres rares.

Abstract : Geminal dianions stabilized by hypervalents phosphors recently aroused a deep interest as carbene precursors for d0 metals and the lanthanides; however, the interactions between the main group elements, as the carbon, and these metals are considered as essentially ionic in nature and poorly directional, whereas the connections between the carbon and the metal in a common carbenic complex are usually described as being directional and partially covalent. The present work aims at synthesizing new complexes of group 3 metals, stabilized by a bis-(diphenylthiophosphinoyl)-methanediide. We intend here firstly to synthesize such species and model their electronic structure, secondly to study their reactivity for a better understanding of the multiple metal-ligand interaction. These studies were led on scandium, then partially widened to the other elements of the group 3: yttrium and lutetium. It emerges from this study that these interactions are directional, of σ and π symmetry, but that they stay in competition with the ab initio stabilization within the free dianionic ligand. This stabilization allows the carbon-metal interaction to adapt according to the other ligands in the coordination sphere. When those last are ionic in character and strong donor, the carbon-metal interaction becomes more ionic as well and the interaction of π symmetry can be broken. The reactivity of those species remains close to that of Schrock type carbenes. Undesirable reactions leading to the deterioration of the ligand were also observed; a more resistant ligand, carrying a phosphine-borane and an oxophosphine functions was proposed. New perspectives in the reactivity of such species were also investigated: transmetallation reactions allowed to reach new complexes featuring interesting magnetic properties, alkyne coupling was performed.
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Marie Fustier-Boutignon. Dianions géminés stabilisés pour la formation de liaisons multiples carbone - terres rares.. Chimie de coordination. Ecole Polytechnique X, 2012. Français. ⟨pastel-00959835⟩

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