Electron localization in the bis-arene complexes [(η-C6H6)2Cr] and [(η-C6H5Me)2Mo]: an investigation by photoelectron spectroscopy with variable photon energy

Abstract

Relative partial photoionization cross sections have been measured for the valence bands of [(η-C6H6)2Cr] and [(η-C6H5Me)2Mo] over the photon energy ranges 24-80 eV ([(η-C6H6)2Cr]) and 24-100 eV ([(η-C6H5Me)2Mo]). Both compounds show pronounced intensity increases of the metal-based ionizations (a-1 1g and e-1 2g) in the region of the np subshell ionization potentials, attribute to nd resonant photoemission following np→nd giant resonant absorption. Shape resonances are also observed in the cross sections of these bands. For [(η-C6H5Me)2Mo], the two resonance processes are almost coincident in photon energy, but can be distinguished more clearly in the [(η-C6H6)2Cr] cross sections. Evidence for metal d-carbon 2pπ covalency in the e1g set of molecular orbitals is found, with features in the cross sections of the metal-based bands correlating with those in the e-1 1g ionizations. The e-1 1u bands show an essentially monotonic cross section decrease with photon energy. © 1992.