Halosilylenoids, stable at room temperature (Tsi)X(2)SiLi (Tsi=C(SiMe(3))(3), X=Br, Cl), were synthesized from the reaction of TsiSiX(3) with lithium naphthalenide. Bromosilylenoid reacted with tBuOH and MeI both at -78 degrees C and at room temperature to give (Tsi)HSiBr(2) and (Tsi)MeSiBr(2), respectively, in high yields; this clearly shows its nucleophilicity. In the reaction of bromosilylenoid with methanol, 2-propanol, and 2,3-dimethyl-1,3-butadiene, the corresponding products, (Tsi)HSi(OMe)(2), (Tsi)HSi(OiPr)Br, and bromo(Tsi)silacyclopent-3-ene, were obtained in high yields; this demonstrates its amphiphilic property, as if bromosilylene would be trapped. Chlorosilylenoid also exhibited both nucleophilic and amphiphilic properties. The (29)Si chemical shifts for (Tsi)Br(2)SiLi, (Tsi)Br(2)SiK, and (Tsi)Cl(2)SiLi were 106, 70, and 87 ppm, respectively.

The reaction of lithium bromosilylenoid with MesLi at -10 °C followed by addition of MgBr 2 gave lithium mesitylsilylenoid as a complex with magnesium bromide that was transmetalated by MgBr 2 at 45 °C in THF to give magnesium silylenoid as a weak MgBr 2 complex of trisylmesitylsilylene. A new magnesium mesitylsilylenoid species was stable at reflux temperature in THF and n-hexane and showed amphiphilic properties in the reaction with 2-propanol, water, and n BuLi, respectively.

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