H SUZUKI, N TOKITOH, R OKAZAKI, J HARADA, K OGAWA, S TOMODA, M GOTO
ORGANOMETALLICS 14 2 1016 - 1022 1995年02月
[査読有り][通常論文] Extremely hindered and stable disilenes Tbt(Mes)Si=Si(Mes)Tbt, ((Z)- and (E)-6; Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phnyl, Mes = 2,4,6-trimethylphenyl) were synthesized by a reductive coupling reaction of the corresponding overcrowded dibromosilane Tbt(Mes)SiBr2 (4) with lithium naphthalenide in THF. The molecular structures of (Z)- and (E)-6 were determined by X-ray crystallographic analysis at 120 K. Compound (Z)-6 crystallizes in the monoclinic space group P2(1)/n with a = 22.212(3) Angstrom, b = 13.368(2) Angstrom, c = 29.725(3) Angstrom, beta = 91.344(9)degrees, V = 8824(2) Angstrom(3), and Z = 4. Compound (E)-6 C10H8 crystallizes in the monoclinic space group P2(1)/c with a = 18.130(3) Angstrom, b = 18.466(3) Angstrom, c = 28.522(2) Angstrom, beta = 95.976(9)degrees, V = 9497(2) Angstrom(3), and Z = 4. The X-ray structures show remarkable pyramidalization around silicon atoms and elongation of the Si-Si double bond (2.195(4) Angstrom for (Z)-6 and 2.228(2) Angstrom for (E)-6), the values of which are the longest ones reported so far for disilenes having carbon substituents on the silicon atoms. Both disilenes were found to be stable for weeks in the open air even in a microcrystalline form, and they were gradually oxidized to afford stereospecifically the (Z)- and (E)-1,3,2,4-dioxadisiletane compounds 10. Compound (Z)-10 crystallizes in the monoclinic space group P2(1)/n with a = 22.420(5) Angstrom, b = 13.458(6) Angstrom, c = 30.417(4) Angstrom, beta = 90.96(1)degrees, V = 9176(4) Angstrom(3), and Z = 4. Reaction of Tbt(t-Bu)SiBr2 (5) with lithium naphthalenide proceeded in a different way to afford the benzosilacyclobutene 11, which was most likely an intramolecular C-H insertion product of the intermediary silylene Tbt(t-Bu)Si: (12).