A NEW REACTIVE SYSTEM FOR CATALYTIC BIS-SILYLATION OF ACETYLENES AND OLEFINS

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(eta3-allyl)CI]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-ds at -20-degrees-C to give the bis-silylation product (Z)-2a in 82% yield together with Pd(PhC=Ph)(PMe2Ph)2 (93%). Treatment of 4a with dimethyl acetylenedicarboxylate (1 equiv) in toluene at -20-degrees-C instantly formed a palladium(0) complex coordinated with bis-silylated olefin, Pd{(X)-(MeO2C)(Me3Si)C=C(SiF2Ph)(CO2Me)}(PMe3)2 (6). The structure of 6 was determined by an X-ray diffraction study. Crystal data for 6 THF : C21H38O4P2F2-Si2Pd.C4H8O, a = 15.585(2) angstrom, b = 12.438(2) angstrom, c = 17.652(2), beta = 93.86(1)-degrees, V = 3413.9(8) angstrom3, monoclinic P2(1)/n, Z = 4.