title: Isolable 2,3-disila-1,3-butadiene from a double sila-Peterson reaction.
abstract: A new 2,3-disila-1,3-butadiene (3) was synthesized as pale yellow crystals by a double sila-Peterson reaction of 1,1,2,2-tetrasilyl-1,2-dilithiodisilane with two equivalents of 2-adamantanone at 0 °C. In the solid state, the two Si=C bonds adopt a synclinal conformation with a dihedral angle of 76.8(1)°. UV/Vis spectra show two distinct absorption bands, assignable to the π(Si=C)→π*(Si=C) transition, at 371 and 322 nm and the former is considerably redshifted compared with that of structurally similar silenes. The 2,3-disilabutadiene isomerizes to the corresponding 1,3-disilabicyclo[1.1.0]butane with the activation parameters of ΔH(≠) = 74.5±5.4 kJ mol(-1) and ΔS(≠) = -71.1±17.1 J mol(-1)  K(-1). DFT studies suggest that the isomerization proceeds through a conrotatory route rather than a disrotatory route. H2O and 9,10-phenanthrenequinone added across each Si=C bond in the 2,3-disila-1,3-butadiene. The UV/Vis spectrum and reactivity of 3 suggest that the interaction between the two Si=C bonds in 3 would be significant but rather small compared with that between Si=Si bonds in a synclinal tetrasilabutadiene.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-aoba, Aoba-ku, Sendai 980-8578 (Japan), Fax: (+81) 22-795-6558.
authors.forename: Daiki
authors.initials: D
authors.lastname: Motomatsu
authors.forename: Shintaro
authors.initials: S
authors.lastname: Ishida
authors.forename: Koichi
authors.initials: K
authors.lastname: Ohno
authors.forename: Takeaki
authors.initials: T
authors.lastname: Iwamoto
keywords: conjugation; sila-Peterson reaction; silenes; silicon