Inner-shell spectroscopies of solid and gaseous alkylidyne tricobalt nonacarbonyl complexes

Abstract

Inner-shell excitation spectra of two alkylidyne tricobalt nonacarbonyl complexes, Co₃(CO)₉C—X (X = Cl, OCH₃), have been recorded at the C 1s, O 1s, Co 2p and Co 3p edges using electron energy-loss (EELS) and photoionisation yield techniques for gas-phase studies and synchrotron radiation photo-ionisation with total electron yield detection for solid-state studies. This comparison was undertaken to provide cross-checks on the experimental techniques; to evaluate the dependence of spectral shape on the detection scheme employed; and to search for effects of intermolecular potentials on the core-excitation spectra of solids. A common set of (core → valence) spectral features are observed by all techniques although some additional minor features are found in specific spectral modes. There are systematic deviations between the oscillator strength for absorption (derived from the EELS data) and that for ionisation (derived from the total ion yield) because the ionisation yield is different from discrete excitation versus continuum ionisation. The ionic fragmentation of the C 1s excited and ionised Co₃(CO)₉CCl complex was investigated using a time-of-flight mass spectrometer for photoion and photoion–photoion coincidence yield studies. Extended Hückel molecular-orbital calculations were used to assist spectral interpretation. The merits of these experimental and computational techniques for systematic investigations of the electronic structure of large organometallic complexes are demonstrated.