Silyl-substituted 1,4-disila(Dewar benzene): New synthesis and unexpected insertion of CO into the Si-Si bond to form a disilyl ketone

The silyl-substituted 1,4-disila(Dewar benzene) (1) was synthesized by the reduction of the corresponding dichloride 2 with 2.2 equiv of KC8 in THF The irradiation of 1 with light of wavelength lambda > 320 nm in THF under a CO atmosphere produced the cyclic disilyl ketone 3 by the insertion of CO into the central Si-Si bond, whereas the photolysis of 1 in cyclohexane-d(12) afforded the silyl-substituted 2,5-disilabenzvalene 4 by intramolecular isomerization.