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. H 2O 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. A new 2,3-disila-1,3-butadiene was synthesized as pale yellow crystals by a double sila-Peterson reaction. Although the two Si=C bonds adopt a synclinal conformation with a dihedral angle of 76.8(1)°, the redshifted longest absorption band maxima assignable to the π(Si=C)→π(Si=C) transition at 371 nm suggests considerable interaction between two Si=C bonds. The 2,3-disila-1,3-butadiene is thermally unstable and isomerizes to 1,3-disilabicyclo[1.1.0]butane (see scheme).
- sila-Peterson reaction