A new reactive system for catalytic bis-silylation of acetylenes and olefins

Article abstract of DOI:10.1021/om00020a042

Reaction of diphenylacetylene (1a) with Me₃SiSiF₂Ph (1 equiv) in toluene in the presence of a palladium catalyst (1 mol %) generated in situ by mixing [Pd(η³-allyl)Cl]₂ and PMe₂Ph (2.2 equiv/Pd) was completed in 1.4 h at room temperature to give the bis-silylation product (Z)-1-(difluorophenylsilyl)-1,2-diphenyl-2-(trimethylsilyl)ethene (2a) in 95% yield. In similar catalytic systems, a variety of acetylenes and olefins, including 3-hexyne, 1-phenyl-1-propyne, phenylacetylene, 1-octyne, norbornene, styrene, and 1-octene, were bis-silylated in 64-96% yields. The highly reactive nature of the present catalytic system was studied in stoichiometric systems. The presumed intermediates trans-Pd(SiMe₃)(SiF₂Ph)L₂ (L = PMe₃ (4a), PMe₂Ph (4b)) were prepared by oxidative addition of Me₃SiSiF₂Ph toward Pd(styrene)L₂ complexes (L = PMe₃ (3a), PMe₂Ph (3b)). Complex 4b reacted with diphenylacetylene (3 equiv) in toluene-d₈ at -20°C to give the bis-silylation product (Z)-2a in 82% yield together with Pd(PhC≡CPh)(PMe₂Ph)₂ (93%). Treatment of 4a with dimethyl acetylenedicarboxylate (1 equiv) in toluene at -20°C instantly formed a palladium(0) complex coordinated with bis-silylated olefin, Pd{(Z)-(MeO₂C)(Me₃Si)C=C(SiF₂Ph)(CO ₂Me)}(PMe₃)₂ (6). The structure of 6 was determined by an X-ray diffraction study. Crystal data for 6·THF: C₂₁H₃₈O₄P₂F₂-Si ₂Pd·C₄H₈O, a = 15.585(2) A?, b = 12.438(2) A?, c = 17.652(2), β = 93.86(1)°, V = 3413.9(8) A?³, monoclinic, P2₁/n, Z = 4.