Electronic Structure of (β-Diketonato)trimethylplatinum(IV) Complexes from UV Photoelectron Spectra and SCF-MS-Xα Calculations

The UV photoelectron spectra of the (β-diketonato)trimethylplatinum(IV) complexes [PtMe₃(acac)]₂ (acac = acetylacetonate), [PtMe₃(tfa)H₂O] (tfa = trifluoroacetylacetonate), [PtMe₃(hfa)H₂O] (hfa = hexafluoroacetylacetonate), and [PtMe₃(tfa)Me₂S] are reported. The valence orbitals responsible for the ionizations have been assigned by using the MS-Xα result for the model compound [PtMe₃(HC(O)CHCOH)] and the ionization shifts from the ligand substitutions. The valence molecular orbitals fall in the order of increasing binding energy π₃ < n_. < Pt-n+ < Pt 5d, Pt-Me in the complexes [PtMe₃(acac)], [PtMe₃(tfa)H₂O], and [PtMe₃(hfa)H₂O] and in the order Pt-S < π₃ ‹ n_ < Pt-n₊ < Pt 5d in the compound [PtMe₃(tfa)Me₂S]. Both photoelectron spectra and the MS-Xα calculation indicate that the Pt 5d electrons are extensively delocalized by interaction with the coordinated ligands.