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978-3-8439-2622-5, Reihe Anorganische Chemie
Mechanistic Insights into Late Transition Metal-Catalyzed Olefin Hydrosilylation and Synthesis of New N-Heterocyclic Carbene and Dinuclear Complexes
97 Seiten, Dissertation Technische Universität München (2016), Softcover, A5
The presented dissertation focuses on mechanistic studies of late transition metal-catalyzed hydrosilylation of olefins and the synthesis and characterization of new N-heterocyclic carbene (NHC) as well as dinuclear complexes.
The first part of this work is dedicated to the hydrosilylation of olefins, which remains one of the most important industrial processes in homogeneous catalysis. Despite the fact that the first platinum-catalyzed protocol was reported in 1957 and the still widely accepted mechanism was established just a few years later, developing a comprehensive mechanistic understanding has been arduous. Therefore, a detailed study of platinum-catalyzed olefin hydrosilylation is presented and a revised Chalk-Harrod mechanism is proposed, in which the rate determining step is reassigned, the addition of isomerization pathways for internal olefins is proposed, and a connection of coordination strength of the olefin and the rate law is derived. An additional study focuses on the iridium-catalyzed hydrosilylation of allyl compounds, which also remains a current challenge in hydrosilylation catalysis. The in-depth investigation reveals the main catalyst deactivation pathways and a fundamental mechanistic picture is deduced.
Since N-heterocyclic carbenes have risen to one of the most important ligand classes in organometallic chemistry, the second part of this thesis is devoted to the synthesis and application of NHC complexes, ranging from hemilabile ligands in iridium complexes applicable in catalytic transfer hydrogenation, to water-soluble palladium compounds for cross-coupling reactions in aqueous media, and phenyl-annulated motifs on platinum in catalytic hydrosilylation.
Achievements in the synthesis of metal-metal-bonded compounds over the past decades have triggered research on establishing applications in many areas from molecular electronics to catalysis and even biology. Therefore, the final contributions of this dissertation are centered on accessing dinuclear complexes and characterizing them with a wide variety of spectroscopic techniques, X-ray crystallography, as well as electrochemical and computational methods. Also the nature of potential metal-metal interactions in the obtained diiridium, dimolybdenum, and dicopper complexes is investigated.