The major aspects of the dissertation are investigations concerning the formation, reactivity and characterization of copper cluster complexes, especially µ4-oxido copper clusters of the formula [Cu4OX6L4] (X=Cl, Br and L=ligand, mainly benzylamine). Investigations of these species are interesting with regard to catalytic applications since multinuclear copper compounds yet have not been investigated sufficiently but seem to be promising candidates because of the higher number of copper centers. In comparison to this experiments concerning the catalytic activity of simple copper salts, especially copper(II) chloride, were carried out. This is interesting because of several reasons: Firstly the mechanism of catalysis with simple copper salts is not clarified for most of the reactions. And secondly a multinuclear active catalyst, which is formed out of simple copper salts is imaginable. This potential relationship was also investigated.Because of that the first part of the work deals with the elucidation of a complex chemical redox equilibrium of simple copper salts, complexes and copper cluster complexes. Hereby it could be shown that simple copper(II) complexes indeed are in a chemical equilibrium with copper cluster complexes. In addition it could be shown that redox processes which led to the formation of copper(I) and copper(II) species took place in solution under specific conditions. Additionally the catalytic activity of µ4-oxido copper clusters concerning the oxygenation of aliphatic CH-bonds with hydrogen peroxide as co-reagent could be shown for the first time. In the second part the formation of copper cluster complexes starting from copper(II) chloride is discussed. Here it could be shown for the first time that under specific conditions copper(II) chloride forms µ4-oxido copper clusters of the formula [Cu4OCl6L4] (L=solvent) in solution. This is especially interesting in regard of the manifold use of copper(II) chloride as catalyst in organic syntheses. Since these solvent clusters also show catalytic activity many of the in the literature proposed mechanisms have to be reviewed.The last part mainly deals with the reactivity of copper(I) chloride towards benzylamine, which did not lead to a cluster formation as preliminary expected but instead to the linear compound [Cu(benzylamine)Cl]4 with copper(I)-copper(I) interactions. Investigations concerning the reactivity towards dioxygen and derivatives did not lead to the identification of any known reaction intermediate.
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