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Silylènes stabilisés par des phosphines : précurseurs de nouveaux cations silyliumylidènes et hétérocycles insaturés

Abstract : This thesis focuses on the reactivity of phosphine stabilized silylenes, and particularly their use as precursors of low-coordinate four-valence-electrons silyliumylidene ions (R-Si:+). The stabilization of those highly reactive species will be considered via the coordination of two Lewis bases at the cationic silicon center featuring formally two empty orbitals. In the first chapter an overview concerning the stabilization and reactivity of silylenes is presented. Particular emphasis has been placed on the description of their electronic properties which are responsible for the stability-reactivity balance of these derivatives. The second chapter concerns the use of phosphine-stabilized silylene complexes for the reversible activation of E-H bonds (E = R3Si, R2P) via oxidative addition/reductive elimination processes, which are classical in organometallic chemistry, but rarely observed for main group element species. The last chapter deals with the synthesis and characterization of silyliumylidene ions (R-Si:+), and particularly we have considered their stabilization using a set of two different L ligands such as phosphines, sulfides, pyridines and N-heterocyclic carbenes NHC. Of special interest, the phosphine/dimethylsulfide-stabilized silyliumylidene cation, thanks to the labile sulfide ligand, presents a very high reactivity with various reagents (olefins, alkynes, silanes,...), leading to the formation of the corresponding silylium cations, intramolecularly-stabilized by a phosphine ligand. These latter, remaining very reactive, are able to activate a second type of substrate. These results clearly show that the sililymilydenes are capable of activating successively two different molecules, which should make it possible to envisage their use as catalysts similarly to transition metal complexes.
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Raphaël Nougué. Silylènes stabilisés par des phosphines : précurseurs de nouveaux cations silyliumylidènes et hétérocycles insaturés. Génie chimique. Université Paul Sabatier - Toulouse III, 2018. Français. ⟨NNT : 2018TOU30021⟩. ⟨tel-02061980⟩



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