High-resolution, uniformly calibrated Fe 2p 3/2 absorption spectra of various Fe(II) and Fe(III) compounds with the metal atom octahedrally coordinated to atomic and molecular ligands are analyzed expecting changes in the absorption spectra due to differences in the formal valence state and in the character of the chemical bond. Particular attention is given to revealing spectral characteristics of the 3dπ-2π(π*) charge transfer (π-back-donation effect) between the iron atom and cyanide ligands.