The He I valence photoelectron spectra in the 6-9-eV ionization region are reported for the following complexes: Mo-(CO)5PMe3, cis-Mo(CO)4(PMe3)2, trans-Mo(CO)4(PMe3)2, fac-Mo(CO)3(PMe3)3, Mo(CO)5PEt3, trans-Mo(CO)4(PEt3)2, Mo(CO)5P-n-Bu3, and trans-Mo(CO)4(P-n-Bu3)2. The observation of vibrational structure due to excitation of a CO stretching mode in several of the spectra aids band assignment. These data are used to test the validity of the model of ligand additivity for determining the energetics of the dπ electrons in octahedral d6 complexes. It is shown that the model successfully correlates the positions, intensities, and number of the ionization bands for the above compounds. A comparison of the results for the complexes of different phosphine ligands indicates that PMe3, PEt3, and P-n-Bu3 are comparable π-acceptors, but that the σ-donor strength increases as PMe3 < PEt3 < P-n-Bu3.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry