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Exploitation de la réactivité de l'or via le design des ligands : stabilisation des intermédiaires réactionnels et développement de nouveaux processus catalytiques Au(I)/Au(III)

Abstract : The present work is an organometallic study concerning the chemistry of gold(I) complexes and their reactivity. Of particular interest was to gain further knowledge on the impact of the ligands employed on the reactivity of gold towards (i) the intermolecular oxidative addition of aryl halides and (ii) the possibility of stabilizing high reactive gold(I) intermediates. In the first part of the manuscript, the intermolecular oxidative addition of aryl halides (iodide and bromide) with molecular gold(I) complexes was investigated in detail. We showed that this organometallic elementary step, usually considered to be impossible for gold, is actually a favorable process when an adequate ligand is employed and two different strategies have been elaborated. The first one consists in the use of a bis-phosphine bidentate ligand that forces a bent geometry around gold, whereas the second strategy implicates the use of a hemi-labile bidentate ligand bearing a soft and a hard donor group. Both strategies were found fruitful, and the gold(III) complexes stemming from oxidative addition reactions were characterized by spectroscopic and structural means. In the second part, having in hands two gold(I) complexes that undergo the oxidative addition reaction, we wanted to go beyond this elementary step. In that objective, we constructed a new Au(I)/Au(III) catalytic cycle involving a sequence of Csp2-X oxidative addition, Csp2-H auration and reductive elimination, allowing the first example of gold-catalyzed direct arylation of arenes with aryl halides. Finally, in the last part, we attempted to stabilize and characterize high reactive gold(I) intermediates, like the a-oxo gold(I) carbenes. This electrophilic species is proposed in many catalytic transformations as key intermediates, but has never been isolated or characterized (in solution or in solid state). The use of a bidentate diphosphine ligand allowed the characterization of the a-oxo gold(I) carbene for the first time by means of multinuclear NMR spectroscopy, X-ray diffraction analysis and high resolution mass spectroscopy (ESI+). We then investigated the reactivity of the a-oxo gold(I) carbene towards insertion and cyclopropanation reactions. Interestingly, the reactivity of the generated gold(I) carbenes can be modulated depending on the electronic properties of the aryl ethyl diazoacetate used.
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Abdallah Zeineddine. Exploitation de la réactivité de l'or via le design des ligands : stabilisation des intermédiaires réactionnels et développement de nouveaux processus catalytiques Au(I)/Au(III). Catalysis. Université Paul Sabatier - Toulouse III, 2017. English. ⟨NNT : 2017TOU30308⟩. ⟨tel-01945748⟩

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