Variable-energy photoelectron spectroscopy of CpM(CO)₃ (M = Mn, Re) and CpFe(CO)₂I

Photoelectron spectra of the valence, inner-valence, and core levels of CpM(CO)₃ (M = Mn, Re) and CpFe(CO)₂I were obtained using He I radiation and synchrotron radiation between 21 eV and 150 eV photon energies. The high-resolution Mn 3p, Fe 3p, and I 4d core level spectra are reported. Broadening of the I 4d spectrum is due to vibrational and ligand field splittings. Observation of the 3p spectra is critical to fully interpreting the np→nd resonance effect in the valence band spectra. This resonance effect is very useful for assigning the metal d orbital bands in the valence spectra. A Xα-SW calculation of CpMn(CO)₃ was used to confirm the assignment of the valence and inner-valence orbitals. The experimental and theoretical branching ratios are in good agreement. The general trend of the metal d orbital ionization potentials for CpML₃ (M = transition metal) complexes is also discussed.