Lichtabsorption und Struktur von Kristallverbindungen der Übergangsmetalle. I. Lichtabsorption und Stuktur der Hydroxide, Halogenide und Hydroxidhalogenide von Kobalt und Nickel

The absorption spectra of the following compounds have been measured: COX2, NIX, (X=Br, C1, F, OH); CoOHX, NiOHX (X=Br, Cl); Co2(OH)3X (X=Br, C1, F), and Ni2(OH)3X (X=C1, F). The observed absorption bands have been correlated with d‐d‐transitions of the metal ion. The coordination polyhedron of these compounds is an octahedron or a distorted octahedron. It was found that the structural symmetry and the symmetry of the crystal field are not always identical. A moderate distortion of the octahedron does not show up in the absorption spectra. Only a strong deformation (e.g. CoOHX) causes an additional splitting of the electronic levels, whereas the spectra of the corresponding distorted Ni compounds match with those of the compounds with only one kind of ligands.