Electronic Structure of Square-Planar cis-Bis(trifluoromethyl)platinum(II) Complexes from UV Photoelectron Spectra and SCF–MS–Xα Calculations

UV photoelectron spectra of cis-[Pt(CF₃)₂L₂] (L₂ = 1,5-cyclooctadiene (COD), Me₂NCH₂CH₂NMe₂ (TMED); L = PEt₃, AsMe₃) are reported, as well as MS–Xα calculations on the model compounds [Pt(CF₃)₂(Ć₂H₄)₂] and cis-[Pt(CF₃)₂(PH₃)₂]. The spectra are assigned by using MS–Xα calculations and by comparison with the spectra of the corresponding dimethylplatinum(II) complexes. The first two ionization bands (with lowest ionization energies) are assigned to platinum–ligand σ orbitals, followed by four bands due to the essentially nonbonding platinum 5d orbitals. The nature of the Pt-CF₃ σ bonding is discussed in terms of MS–Xα results. In contrast to the Pt–CH₃ σ bonds, the Pt–CF₃ σ bonds have a significant C 2s and C–F antibonding character.