Open-shell cobalt complexes with redox-active ligands Electronic structure and nitrene transfer reactivity

Homogeneous catalysis plays a pivotal role in the selective formation of e.g. bioactive molecules and plastics. Especially the formation of C‒N bonds via homogeneously catalyzed nitrene (N-group) transfer is a desirable process, as it allows for the direct functionalization of unactivated substrates. Nature is able to perform a plethora of similar chemical transformations under mild reaction conditions and with high selectivity by usage of inter alia radical-type (single-electron) reactivity and redox-active ligands in conjunction with abundant first row transition metals.
In this dissertation I draw inspiration from Nature and describe the synthesis, characterization and application of redox-active ligands and nitrene radicals in the coordination sphere of cobalt. The results encompass unconventional electronic structures and the applicability of the studied systems in the formation of C‒N and S=N bonds via fundamentally new mechanisms. Most notably, new roles for the metal, redox-active ligand and nitrene radical are described; during nitrene radical transfer the metal acts as a spin shuttle, the redox-active ligand as a transient electron acceptor and the nitrene radical as a nucleophile. This allowed for the development of highly chemoselective nitrene transfer reactions under mild, and even aerobic, reaction conditions. The results described in this dissertation pave the way to other catalytic radical-type reactions under similar conditions and expanded on the commonly accepted mechanisms via which these reactions proceed.