Photoelectron spectroscopy of organotransition metal complexes

Abstract

A brief introduction to photoelectron spectroscopy (PES) and its use in connection with molecular orbital (MO) calculations is given. A series of diene-tricarbonyliron and -tricarbonylruthenium, and related complexes, has been synthesised. Previous studies of their molecular and electronic structure are reviewed. The UV photo-electron spectra of these complexes, together with those of the diene ligands are presented and assigned with the aid of qualitative MO diagrams and existing MO calculations. Bonding of the diene to the tricarbonylmetal unit is discussed and an attempt is made to correlate the diene conformation within the complex to UV photo electron spectro-scopic data. Hel and Hell UV photoelectron spectra are presented for the metallocenes of the first row transition elements (V to Ni). Molecular and electronic structures and electronic ground states implied from spectroscopic data are reviewed. The PE spectra of open shell molecules are discussed, and the spectra of the metallocenes are assigned with the aid of previous assignments, MO, and crystal field theories. Use is made of the knowledge that ionisation cross sections for an orbital of particular atomic character change relative to each other for ionisation by photons of different energy. Relative ionisation cross sections are calculated from experimental data.Hel and Hell PE spectra are obtained for a series of diene-cyclopentadieny lM (M = Co, Rh, Ir) complexes. The expected similarity of spectra of the rhodium and iridium analogues is noted, and an unexpected marked difference in the PE spectra of rhodium and cobalt analogues is observed. This is discussed in relation to bonding and with reference to noted differences in chemical reactivity of some other similar rhodium/cobalt analogues. Assignments of the PE spectra are made with the help of qualitative MO diagrams. The PE spectra of two cyclopentadienyldicarbonylM (M = Co, Rh) Complexes are compared. The instrumentation used for obtaining the photoelectron spectra is discussed in detail in Appendix 1 .