Gas phase photoelectron spectra of d- and f-block organometallic compounds

Organometallic compounds display a wide variety of non-classical bonding interactions largely as a result of the ability of the π-electrons of organic groups to form covalent bonds with d-block transition metals. Photoelectron spectroscopy has proved an invaluable tool in confirming and extending ideas on the nature of these interactions. Studies reported are all on gas phase species for which detailed information on the valence electrons may be obtained. Relative intensity changes observed on varying the ionizing radiation between He (1) and He (11) are of considerable assistance in assigning photoelectron bands and in providing information on the localization of the molecular orbitals from which the associated electrons are ionized. Most assignments are discussed in relation to simple, qualitative molecular orbital schemes. Comparisons are made between bonding of different metals and different organic groups. Particular emphasis is placed, where information is available, on the differences between d- and f-block metals in this class of compounds. The detailed understanding which has resulted from a combination of photoelectron spectroscopy and theoretical studies in this area has led to reliable models which should prove useful to the experimental chemist.