Oxidative Addition of Silicon−Halogen Bonds to Platinum(0) Complexes and Reactivities of the Resulting Silylplatinum Species

Abstract

Oxidative addition of the silicon−halogen bonds of halosilanes R3Si−X (X = Cl, Br, I) to platinum(0) complexes PtLn (L = tertiary phosphine) yielded trans-R3SiPtXL2 species. Halosilanes exhibited the following orders of reactivities: for Me3SiX, X = Cl (no reaction) << Br < I, and for Me4-nSiCln, n = 1 (no reaction) << 2 < 3. The reactivities of platinum complexes increased in the order of Pt(PPh3)4, Pt[Ph2P(CH2)2PPh2]2 (no reactions) << Pt(PMe2Ph)4 < Pt(PMe3)4 < Pt(PEt3)4. Coordinately unsaturated Pt(PEt3)3 was more reactive than Pt(PEt3)4. Me3SiSiMe2I also underwent addition at the Si−I bond to Pt(PEt3)3 with the Si-Si bond being intact to form trans-Me3SiMe2SiPtI(PEt3)2. Treatment of trans-Me3SiPtBr(PEt3)2 (2a) with a phosphine (PEt3, PPh3) resulted in reductive elimination of Me3SiBr. The reaction of 2a with styrene gave PhCHCHSiMe3, although the major part of the Me3Si moiety was eliminated as Me3SiBr. Silyl group exchange of 2a or trans-Me3SiPtI(PEt3)2 cleanly took place upon treatment with the hydrosilane R3SiH (Me2PhSiH, MePhSiH2) to provide trans-R3SiPtX(PEt3)2 (X = Br, I). Transmetalation between 2a and Et2Zn or Ph2Hg respectively yielded Me3SiEt or Me3SiPh in a smooth reaction. 1H, 13C, 29Si, 31P, and 195Pt NMR spectra of the resulting silylplatinum species are discussed in terms of the trans and cis influences and the electronegativity of the ligated groups.