He(I) photoelectron spectra of some π-arene complexes

Abstract

The He(1) photoelectron spectra of (x-C6H&Cr, (x-C6HsCH&Cr, (~-c&)(n-csH~)Mn and (IT-C~H~)(X-CSHS)C~ have been measured and their electronlc structure 1s discussed in the light of the ionization energy data.Studies on bis-n-arene complexes have been mainly concerned with bis-n-benzene chromium. This compound is isoelectronic with ferrocene but shows a very different chemistry, and this has been attributed to its ease of 0xidation.l Approximate M.O. calculations * and various spectroscopic studies on bis-71-benzenechromium have raised the question of the relative energies of the upper a,, and eZg levels. Berry proposed the order a,, <e2, on the basis of the electronic spectrum, but added in proof that the opposite order could also be explained. E.s.r. studies on the bis-nbenzenechromium(1) cation 5-7 indicated the order eZS < a l g , as did the electronic spectrum.s By analogy, it was suggested that the order of the energy levels in bis-71-benzenechromium was the same. An ordering of ligand field orbital energies which do not include the effects of interelectronic repulsion within the perturbed d-shell does not necessarily correspond to an ordering obtained by a M.O. calculation or by photoelectron spectroscopy.We have measured the He(1) photoelectron spectra of (n-C6H&Cr, further the electronic structure of these n-arene complexes and to compare n-benzene and the n-cyclopentadienyl radical as ligands.(~FC&CH~)~CT, (7'C-C6H6)(X-CgH5)Cr and (n-CsH&n-C5H&h in order to study

In situ formation and electron-spectroscopic study of bis(arene) V and Cr compounds on a graphite surface

“…Figure 5 shows data for a thin layer of Tol ice and for the same layer after depositing $0.10 ML of Cr. This effect, which is clearly seen in a comparison of gas-phase UPS data 54 for CrBz 2 and Cr(Tol) 2 , appears in Fig. There are, to our knowledge, no published UPS data for toluene ice; however, the results can be discussed with reference to HeI-excited gas-phase spectra.…”

The bonding in some bis(arene)chromium compounds as indicated by U.V. photoelectron spectroscopy

“…Using Figure 1 and the previous assignments for dibenzene chromium, 4 , 5 the first (-4.9 -6.7 eV) and second (-5.7 -7.7 eV) peaks are assigned to the production of the 2Alg and 2 F2g metal-localized states, respectively, while the third peak (-8.5 -11.0 eV), which sometimes exhibits perceptible splitting (vide Infra), is assigned to electron ejections from the lelg 5 and leIn ligand-centered MO's. The relative photoionization cross sections for these assignments are crudely commensurate with the relative orbital degeneracies.…”

The Electronic Structure of Closed Shell Metallocenes in the Ground State and in the Cationic Hole-States

“…The He (I) PE spectrum of the mixed sandwich 4 has been recorded by Evans et al [16]. Five separate maxima can be discriminated in the outer valence region below 11 eV.…”

“…Three bands with maxima at 5.45, 6.46 and 9.80 eV are found in the low energy region of 2 [14][15][16]. The third peak has a low energy shoulder at 9.56 eV.…”

“…Three complexes with occupied 3d orbitals have been considered: bisbenzene chromium (2), ferrocene (3) and the mixed sandwich cyclopentadienyl benzene manganese (4). The PE spectra of these compounds have been measured by several groups (1: [13], 2: [14][15][16], 3: [13,17,18] and 4: [16]). Within the series 1-4 only the PE spectra of 2 [14] and 3 [2,19,20] have been discussed on the basis of computational results (zlSCF calculations), the PE data of 1 and 4 have 0340-4811 / 82 / 1000-1193 $ 01.30/0.…”