Synthese und Anwendung neuer, Cyclophan-basierter N-heterocyclischer Carbene sowie Studien zur Darstellung cyclischer bismetallischer Amonoylid-Carbenkomplexe

Abstract

A new synthetic route to N-heterocyclic carbenes (NHCs) with cyclophanic architecture is described. Using this approach, the electronic and structural parameters of an imidazopyridine-based carbene could be uncoupled. The electronic cross-talk between the cyclophane-layers made it possible to change the electronic properties without any constitutional redesign. Although the s-donorproperties of the cyclophane-based carbene is comparable to its planar cousin, the results of theoretical (DFT-calculations) as well as experimental (IR, CV, X-ray) studies suggested that it is much easier to tune its p-acceptor-properties. Furthermore, reactivity data demonstrated that the outcome of three mechanistically distinct gold-catalyzed reactions was determined by changing the p-acceptor-properties of the particular NHC that is used. The second part of this dissertation deals with the synthesis and characterization of phosphorusbased aminoylid carbenes (AYCs) and with the synthesis of homo- as well as heteronuclear bimetallic AYCs. Theoretical (DFT), experimental (CV, IR) as well as reactivity data gave some insights into the ambivalent electronic properties of AYCs. On the one hand IR-data indicated that this type of carbene is one of the strongest s-donors known nowadays. On the other hand reactivity data, e. g. of a gold (I) catalyzed enallene cycloaddition, also gave evidence for their distinctive p-acceptorproperties. Using a silver-carbene approach several different mono- and heteronuclear bimetallic AYCs could be synthesized.