The electronic structure in 3d transition metal complexes: Can we measure oxidation states?

We discuss the information on the electronic structure that can be obtained by K-shell absorption and emission spectroscopy in systems that contain 3d transition metals. We remind the reader that the chemical sensitivity of the X-ray absorption near edge structure (XANES) is strongly influenced by the local geometry. The X-ray fluorescence is mostly sensitive to the electronic structure and thus complementary to XANES.