INNER-SHELL EXCITATION OF ORGANOIRON COMPOUNDS BY ELECTRON-IMPACT

Oscillator strengths for the inner-shell excitation (C 1s, O 1s, Fe 2p, and Fe 3p) of eight gas-phase organoiron complexes Fe(CO)5, Fe2(CO)9, RFe(CO)3 (R = C4H6, c-C6H8, c-C8H8), and CpFeCpR' (R' = H, C2H3, C4H9) have been derived from electron energy loss spectra recorded under electric dipole scattering conditions. Tentative spectral assignments have been made based upon comparison to the spectra of free ligands and to previous gas-phase studies of related organometallic species. The spectra provide insight into how core excitation spectroscopy reflects the iron-ligand bonding in these complexes. The C 1s, O 1s, and Fe np spectra of related molecules in a series (e.g., carbonyl complexes or ferrocene derivatives) have a similar shape, suggesting similar origins of the spectral features. Small variations through each series have been interpreted in terms of changes in the electronic structure associated with changing substituents. The sensitivity of core spectra to ligand-ligand electronic interaction has been assessed through comparisons to spectral simulations based on the sums of experimental spectra of free ligands and single-ligand complexes. Spectral simulations based on extended Huckel (EHMO) calculations have also been carried out for C 1s and Fe 2p excitation in Fe(CO)5 and Fe2(CO)9. The Fe 2p spectra are surprisingly sensitive to the type of ligands present in the complexes.