Inner-shell electron energy loss spectroscopy of organometallic compounds

Absolute photoabsorption oscillator strengths for inner-shell excitation of gas-phase 3d transition metal carbonyls (Mn..Ni) metallocenes (Fe,Co,Ni) and species with mixed carbonyl and it-bonded ligands (c-(C6H8)Fe(CO)3 (C-(C6h8) = 1,3-cyclohexadiene) and CpCo(CO2) (Cp = c-C5H5, cyclopentadienyl) have been derived from inelastic electron scattering spectra recorded under conditions dominated by electric dipole transitions. The main features of the C 1s and O 1s spectra of the metal carbonyls are very similar to those of CO. A reduction of the C 1s-- > π∗ oscillator strength is observed, which can be used as a semi-quantitative measure of the extent of dπ-pπ backbonding. The C 1s spectra of c-(C6H8)Fe(CO)3 CpCO(CO)2 are compared to weighted sums of the spectra of species containing the individual ligands. Such comparisons provide a sensitive probe of the effects of ligand-ligand interactions on the electronic structure of organometallic compounds.