UV Photoelectron Spectra of Some Bent Bis(η⁵ -cyclopentadienyl) Niobium and Tantalum Complexes

Abstract

<jats:title>Abstract</jats:title><jats:p> He(I) and He(II) photoelectron spectra are reported for (η<jats:sup>5</jats:sup>-C<jats:sub>5</jats:sub>H<jats:sub>5</jats:sub>)<jats:sub>2</jats:sub>MLX (M = Nb, Ta; L = H, CO; X - propene, 1-butene, propyl) and some methylcyclopentadienyl deriva-tives. Also the spectra of some π-allyl and dihalide complexes are reported. Unambiguous assignments could be made of the metal d a<jats:sub>1</jats:sub> orbital, the Cp orbitals, the olefin π ionization and the M-hydride and π-allyl orbitals. Very regular trends are observed in the ionization energies upon substitution of the ligands. The olefin π ionization is found at very low energy indicating that the π backbonding to the olefin is very important. He(I)/He(II) cross section differences show clearly differences in metal character of the various M.O.'s.</jats:p>