ELECTRONIC-STRUCTURE OF OS(CO)(4)L (L=CO, PME(3)) STUDIED BY VARIABLE-ENERGY PHOTOELECTRON-SPECTROSCOPY

High-resolution variable-energy photoelectron spectra of Os(CO)(5) and Os(CO)(4)PMe(3) are reported. Using variable-energy synchrotron radia tion, both the metal 5p --> 5d resonance and the Cooper minimum effect are observed on the osmium 5d orbitals, and they have been successful ly used to assign the osmium 5d-based bands. The X alpha-SW calculatio n for Os(CO)(5) is used to assign the valence level molecular orbitals . Experimental branching ratios of Os(CO)(5) agree well with the theor etical results from both X alpha-SW and Gelius methods. The electronic structure of Os(CO)(5), from the present study is shown to be similar to that of Fe(CO)(5), both of which have a trigonal-bipyramidal struc ture. The binding energies of the Os 5p core level have been determine d, which are shown to be important in the observation of 5p --> 5d res onances. Both vibrational and ligand field splittings are shown to be important in the line broadening in the high-resolution Os 4f core lev el spectra. The chemical shifts of valence and core levels for Os(CO)( 5) and of Os(CO)(4)PMe(3) are compared.