The He(1a) photoelectron spectra of [M(C6H,Me,-1,3,5)(C0),] and [M(C,H,)(CO),] ( M = Cr, Mo, or W) are reported. The metal &orbital and ligand x orbital ionization energies are assigned and discussed. THE U.V. photoelectron (p.e.) spectra of several Group 6A organometallic complexes have been reported.l-' Of these studies, two report the p.e. spectra for the complete triad with a given set of ligands, [M(PF,),] and [M(CO) J.2 In both cases the first ionization energy (i.e.) corresponds to ionization from metal d orbitals, and has only a very slight dependence on the metal. Herein we present the He(1a) p.e. spectra of q-cyclohepta-l,3 ,5triene-and q-mesitylene-tricarbonylmetal complexes for M = Cr, Mo, and W. These complexes allow a comparison of the metal d i.e.s as well as the effect of the metal on the i.e.s of the hydrocarbon x orbitals.
EXPERIMENTALThe p.e. spectra were obtained on a spectrometer of the Turner type,8 incorporating a 7424 ( 10-cm) electrostatic cylindrical condenser analyzer. The spectra were excited with He(1a) (21.22 eV) t photon radiation. The ionization energies ( f 0.05 eV) were inferred from internal calibration with xenon and argon. Mass spectra were recorded on a Varian CH-5D instrument using a Varian combined field desorption-electron impact (f .d.-e.i.) source. Acetone was t Throughout this paper: 1 eV x 1.60 x J ; 1 Torr = (101 325/760) Pa.
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