Experimentelle und theoretische Studien von Metall-Bispidinkomplexen

The overall topic of this work is the synthesis, experimental and theoretical investigation of various metal bispidine complexes. In the first part of this thesis (chap. 3) the synthesis of several cobalt(II) bispidine complexes and their oxidation with molecular oxygen is described. The formation of a species with a deprotonated nitrogen donor was characterized by X-ray crystallography. Furthermore, magnetic properties of cobalt(II) bispidine complexes were studied. The aerobic methanogenesis of different iron(IV) oxido compounds supported by bispidine ligands is demonstrated in the second part (chap. 4). Moreover, a previously postulated reaction mechanism was substantiated by several techniques. The synthesis and characterization of ruthenium(II) complexes with a range of bispidine ligands is presented in the third part of this thesis (chap. 5). Within this series, one complex was outstanding due to an unexpected color change in solution and was studied in depth. Additionally, a ruthenium(II) half-sandwich complex was used to expand the family of bispidine complexes by introducing an additional coordination sphere. Chapter six focuses on the synthesis of bispidine ligands containing dicarboxylic acids as donor functionalities. The preparation of ligand scaffolds which incorporate malonic acid was examined and this procedure was expanded to the corresponding ligands featuring succinic and glutaric acid. A detailed DFT study investigating the correlation of the pKa values of various donors in the bispidine ligand scaffold and their effect on the spin state of octahedral iron(IV) oxido complexes is described in the fifth and final art of this thesis (chap. 7). Further DFT calculations were conducted to design of a seven-coordinate bispidine ligand system, which is highly promising to promote the formation of low-spin iron(IV) and ruthenium(IV) oxido compounds.