Bandeau LBPB

Topics

1 Ambiphilic derivatives: Unusual coordination modes and Catalytic applications (G. Bouhadir)

 

Over the last decade, we have developed ambiphilic compounds combining donor (D) and acceptor (A) sites. One of our main interest has been to explore and develop the ligand behavior of these compounds towards transition metals (M). Several coordination modes have been evidenced depending on the role of the acceptor site. A particular interest has been devoted to the ability of the acceptor site (i) to coordinate the transition metal as sigma-acceptor ligand, and (ii) to interact with a metal co-ligand eventually up to its abstraction to give zwitterionic complexes in which the metal center is electrophilic. The coordination behavior and the unusual interactions (nature, strength, characteristic features …) have been assessed and rationalized by theoretical studies. Currently, we are studying new ambiphilic ligands by varying the nature of the acceptor/donor sites and the linker. In this context, we aim to take profit of the presence of the acceptor site in the coordination sphere of the metal to assist the activation of H-E (E = H, BR2, SiR3) and/or C-X (X = Cl, F, …) sigma bonds.

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2 Chemistry of the coinage metals (A. Amgoune)

 

Métaux du groupe 11

Our research program on coinage metal chemistry aims to gain a profound knowledge on the coordination chemistry and reactivity of these metals, in particular gold. We seek to design and develop new well-defined gold(I) and gold(III) complexes for applications in organic synthesis and materials. Homogeneous gold catalysis has developed very rapidly over the last decades, to the extent that gold complexes initially considered as inert species are now among the most efficient catalytic systems in organic synthesis. Consequently, an increasing interest was directed towards the understanding of the fundamental reactivity of gold complexes. However, in most of gold catalyzed processes developed to date, gold is used as a simple Lewis acidic catalyst for electrophilic activation of p-CC bonds. In striking contrast with the rich reactivity patterns of the other transition metals, very little is known about the reactivity of gold complexes towards important elementary steps in transition metal catalysis. We are particularly interested in investigating the reactivity of gold complexes towards oxidative addition/reductive elimination and migratory insertion processes. Thanks to a rational ligand design approach we recently evidenced that gold is able to promote unprecedented transformations such as oxidative addition of Si-Si, C-C and Csp2-X bonds, and migratory insertion of alkynes, allenes and alkenes. These common elementary steps are common with most transition metals, but were unprecedented with gold.

 

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3 Pincer complexes, Non-innocent ligands and Cooperative catalysis (B. Martin-Vaca, J. Monot, G. Bouhadir)

 

Pince 1
Pince 2

Over the last decade, pincer complexes have attracted an upsurge of interest from the scientific community. Tuning the structure of the pincer ligands has given rise to a huge variety of complexes, from which those promoting original catalytic transformations involving metal/ligand cooperation can be highlighted. In this context, we have developed an original family based on the indene skeleton which can adopt for the first time a planar h1-coordination. The central C2-M bond is a single s bond and the p contribution is very weak. The presence of an important electronic density over the indenyl backbone, especially on C1 and C3, suggests a potential participation of the ligand during some chemical transformations. Indeed, these ligands exhibit a non-innocent character demonstrated by their participation in the stoichiometric activation of organic and metallic electrophilic partners. This non-innocent character has then been successfully applied in metal/ligand cooperative catalysis. The cycloisomerization of alkynoic acids and alkynylamides takes place in the presence of palladium indenediide complexes without involvement of an external base. Recently, the group described another family of pincer ligands, namely diphosphine/phosphide oxides. Remarkably, the coordination of the two phosphine arms promotes the activation of central P(O)-C/H bonds. These oxidative additions involves only low activation barriers and directly lead to the corresponding PP(O)P pincer complexes.

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4 Biodegradables polymers : synthesis and applications (B. Martin-Vaca, A. Amgoune)

 

Polymer

Polyester and polycarbonate synthetic biodegradable polymers have attracted considerable interest over the last decades not only for the encapsulation and sustained release of drugs but also for packaging and applications as additives. Among the preparation process of these polymers, the ring-opening polymerization (ROP) of lactones or cyclic carbonates allows good control of the polymer structure. In this context, we are developing new tools as well as original and efficient technics for the controlled preparation of well-defined biodegradable polymers under mild conditions. Our work combines different aspects: (i) the development of new organic and/or metallic catalytic systems, including dual organic/metallic catalytic systems, (ii) the synthesis of functionalized monomers, (iii) the preparation of (co)polymer of controlled architectures. From an application standpoint, we are searching to take profit of new copolymers for the formulation of bioactive ingredients and as nano-structured materials for microelectronics.

We demonstrated the efficiency of sulfonic, phosphoric and phosphoramidic acids for the controlled polymerization of lactide, e-caprolactone and trimethylene carbonate. In addition, we have recently succeeded in the development of a new catalytic system combining an amine and a Lewis acid for the synthesis of cyclic polyesters. Besides the applications, we are very interested in understanding the mode of action of the new catalysts and the polymerization mechanism.

 

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