Valence band photoelectron spectra of transition-metal cyanides

X-ray photoelectron spectra of the valence bands of NaCN, Li₄Fe(CN)₆, Li₃Fe(CN)₆, Ni(CN)₂, Li₂Pt(CN)₄ and LiSCN have been measured and interpreted. Normalization of the valence-band intensities by equalization of the nitrogen is intensities made it possible to distinguish between cyanide and transition-metal bands. The spectrum of CN^? is similar to that of the iso-electronic molecules N₂ and CO. The transition-metal bands occur at a lower binding energy than the CN^? bands and do not show structure. From the intensities we conclude that much less mixing of the metal and ligand orbitals takes place than indicated by recent MO calculations.