Dissertation

|3.1 Brominated Phenanthrolines - A Gate to new Bridging Ligands|
procedures. [128] Using this starting material and two equivalents of phenBr 2 in a microwave
reaction in dry DMF according to an adapted literature procedure the formation of a blue, almost
insoluble compound was observed. After the removal of the solvent and washing with water it was
possible to extract the solid with methylene chloride and to precipitate the product with ether.
Characterization of the solid by 1 H-NMR spectroscopy in CD 2 Cl 2 exhibited two sets of three
signals in the aromatic region of the spectrum with partly very far low-field shifted signals which
corresponds to the protons in the 2,9-positions at the corresponding phenanthroline halves.
Carbon-NMR spectroscopy as well as mass spectroscopy could not be applied due to the poor
solubility in the applied solvents. Slow recrystallization from dichloromethane yielded black
crystals which were taken for X-ray diffraction experiments (compare figure 47). A detailed
discussion follows in section 3.1.3 on page 69 ff.
Figure 47: ORTEP representations of the molecular structures of Ru(phenBr 2 ) 2 Cl 2 (left) and the
homoleptic complex Ru(phenBr 2 ) 3 (right). Counter ions, coordinated solvent and hydrogen atoms
were omitted for clarity. Ellipsoids were drawn at 50% level.
If the same reaction was performed with tree equivalents of phenBr 2 in a mixture of ethanol/water
over the period of 16 hours at reflux temperatures, the formation of a red solution was observed.
Precipitation of the PF 6 -salt yielded the trishomoleptic complex Ru(phenBr 2 ) 3 in good yields.
Hydrogen NMR spectroscopy revealed a very simple spectrum with three signals in the aromatic
region due to the high symmetry of this complex. In the 13 C-NMR spectrum all six chemically
|67|