INNER-SHELL SPECTROSCOPIES OF SOLID AND GASEOUS ALKYLIDYNE TRICOBALT NONACARBONYL COMPLEXES

Inner-shell excitation spectra of two alkylidyne tricobalt nonacarbony l complexes, Co3(CO)9C-X (X = Cl, OCH3), have been recorded at the C 1 s, O 1s, Co 2p and Co 3p edges using electron energy-loss (EELS) and p hotoionisation yield techniques for gas-phase studies and synchrotron radiation photo-ionisation with total electron yield detection for sol id-state studies. This comparison was undertaken to provide cross-chec ks on the experimental techniques; to evaluate the dependence of spect ral 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 sp ecific spectral modes. There are systematic deviations between the osc illator strength for absorption (derived from the EELS data) and that for ionisation (derived from the total ion yield) because the ionisati on yield is different from discrete excitation versus continuum ionisa tion. The ionic fragmentation of the C 1s excited and ionised Co3(CO)9 CCl complex was investigated using a time-of-flight mass spectrometer for photoion and photoion-photoion coincidence yield studies. Extended Huckel molecular-orbital calculations were used to assist spectral in terpretation. The merits of these experimental and computational techn iques for systematic investigations of the electronic structure of lar ge organometallic complexes are demonstrated.