ELECTRONIC-STRUCTURE OF 20-ELECTRON BIS(CYCLOPENTADIENYL)-METAL OXO COMPOUNDS OF GROUP-6 - INVESTIGATION BY PHOTOELECTRON-SPECTROSCOPY

The He I and He II photoelectron spectra have been recorded for [Mo(et a-C(5)H(4)Me)(2)O], [W(eta-C(5)H(4)Me)(2)O] and [W(eta-C(5)Me(5))(2)O] . All show two low-ionization-energy bands, the lowest being assigned to the two metal d electrons and the second to an orbital based primar ily on the cyclopentadienyl rings and an oxygen 2p orbital. Other cycl opentadienyl ionization bands and metal-oxygen bonding ionizations are also identified. The spectra confirm the SCF-X alpha-SW bonding model presented previously. Extended-Huckel calculations, which are in agre ement with the SCF-X alpha-SW calculations, have been used to model th e orbital interactions. The metal-oxygen bonding and the nucleophilic character of the molecules is discussed in the light of the spectrosco pic and theoretical results.