A Theoretical Study of an Unusual Y-Shaped Three-Coordinate Pt Complex: Pt(0) σ-Disilane Complex or Pt(II) Disilyl Complex?

The unusual Y-shaped structure of the recently reported three-coordinate Pt complex Pt[NHC(Dip)2](SiMe2Ph)2 (NHC = N-heterocyclic carbene; Dip = 2,6-diisopropylphenyl) was considered a snapshot of the reductive elimination of disilane. A density functional theory study indicates that this structure arises from the strong trans influence of the extremely σ-donating carbene and silyl ligands. Though this complex can be understood to be a Pt(II) disilyl complex bearing a distorted geometry due to the Jahn–Teller effect, its 195Pt NMR chemical shift is considerably different from those of Pt(II) complexes but close to those of typical Pt(0) complexes. Its Si···Si bonding interaction is ∼50% of the usual energy of a Si–Si single bond. The interaction between the Pt center and the (SiMe2Ph)2 moiety can be understood in terms of donation and back-donation interactions of the Si–Si σ-bonding and σ*-antibonding molecular orbitals with the Pt center. Thus, we conclude that this is likely a Pt(0) σ-disilane complex ...