The He I photoelectron spectra of Cr(CO)5CS, W(CO)5CS, and η-C5H5Mn(CO)2CS have been obtained. It is observed that the ionizations which are associated predominantly with the highest occupied σ and π levels of the thiocarbonyl ligand are clearly separated from the other ionizations of these complexes and display quite different ionization band envelopes. The remaining ionization bands, of these complexes are comparable to the bands observed in the ionization spectra of the corresponding carbonyl complexes. Molecular orbital calculations were performed on the chromium and manganese species. Besides predicting the correct order for the ionizations, the calculations are highly successful in giving a quantitative account of observed trends in ionization potentials between the carbonyl complexes and the thiocarbonyl complexes. As suspected, the thiocarbonyl ligand is found to be a better π-electron acceptor than the carbonyl ligand. However, consideration of this factor alone does not account for the observed trends in ionization potentials between carbonyl and thiocarbonyl complexes. The occupied thiocarbonyl σ and π levels also interact more strongly with the metal, and the electron density has increased at the carbon of the thiocarbonyl group. These factors have important implications for the properties of thiocarbonyl complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry