The interactions between ligands and transition metals have been an essential subject in inorganic chemistry. Other than the commonly known L-type (two-electron donors) and X-type ligands (one-electron donors), Z-type ligands (two-electron acceptors) have begun to surface in the past decade. Capable of drawing a pair of d-electrons away from a metal, Z-ligands affect the electronic structures of transition metals leading to fascinating properties as well as reactivity. In particular, recent advance in Z-ligand chemistry have resulted in the discovery of transition metal borane complexes featuring metal → boron interactions. Owing to the presence of a metal → boron interaction which stabilizes the low valent state, these complexes have been shown to activate small molecules such as H2, CO2, and CHCl3. Further, the concept of Z-ligand has been extended to s- and d-block Lewis acids. In spite of these achievements, Z-ligands that contain Group 14-16 elements as Lewis acids remain scarce and relatively unexplored. For this reason, we have launched a series of investigations targeting complexes with transition metal → Group 14-16 interactions. These investigations have allowed us to synthesize a series of novel complexes with palladium, platinum, or gold as metallobasic late transition metals and tin, antimony, bismuth, and tellurium as Lewis acids. The transition metal → Lewis acid interactions of these complexes, which are supported by o-phosphinophenylene, 1,8-naphthalenediyl or 8-quinolinyl buttresses, have been established experimentally and theoretically. Further, the reactivity of these complexes toward anions and oxidants has also been explored. These experiments have led to the discovery of tellurium-platinum complexes that sustain reversible two-electron redox processes including the photo-reductive elimination of chlorine. Other noteworthy outcomes of this research include the isolation of the first telluroxanyl-metal complex as well as the discovery of complexes with HgII → SbV interactions.

Une nouvelle famille de précatalyseurs à base d'lr(lll) a été découverte. La facilité de leur préparation, leur remarquable stabilité, et surtout leur excellente efficacité catalytique dans plusieurs réactions, c.-à-d. la 0-silylation d'alcools, l'hydrosilylation de fonctions CO et CN et l'activation de la liaison C-F, constituent un ensemble de propriétés que d'autres précatalyseurs organométalliques similaires connus à ce jour ne possèdent pas. Le fait le plus significatif est la mise en évidence expérimentale et théorique que les espèces catalytiques impliquées fonctionnement comme une paire de Lewis du type donneur-accepteur [lr(lll)H]-->[SiR3]. Dans ce cas le ligand silylium doit être considéré comme un ligand Z en appliquant le formalisme de Green, ce qui suggère un état d'oxidation formel de +Ill pour l'atome d'iridium. Cette thèse a contribué à une meilleure compréhension de la chimie du silylium appliquée à la chimie organométallique, et a abouti à l'émergence d'un nouveau champ de recherche qui pourra permettre l'élaboration de nouveaux précatalyseurs multicompétents. / A new family of highly active iridacyclic lr(lll) precatalysts has been discovered. Notably, these ionic iridacycles are very stable so that their handling under air whether in solution or as solid powder is possible. The relative simplicity of their molecular structures allows their preparation on gram scale through a very simple and convenient synthetic protocol. We identified important iridium-silane intermediates involved in the catalysis of various reactions, e.g. the 0-silylation of alcohols, the hydrosilylation of CO and CN functions, and the activation of the C(sp3)-F bond of fluorocarbons. Experimental and theoretical studies of these intermediates point towards a Lewis donor-acceptor structural formulation of the type [lr(lll)H]-->[SiR3]. These results constitute a significant contribution to the design of future multicompetent precatalysts, and provide an original insight to the bonding within the Si-lr-H motif by considering the silylium ion [SiR3]+ as a Z-type ligand rather than a "traditional" X ligand.