Disilenyl Silylene Reactivity of a Cyclotrisilene

The highly reactive silicon congeners of cyclopropene, cyclotrisilenes (c-Si₃ R₄ ), typically undergo either π-addition to the Si=Si double bond or σ-insertion into the Si-Si single bond. In contrast, treatment of c-Si₃ Tip₄ (Tip=2,4,6-ⁱ Pr₃ C₆ H₂ ) with styrene and benzil results in ring opening of the three-membered ring to formally yield the [1+2]- and [1+4] cycloaddition product of the isomeric disilenyl silylene to the C=C bond and the 1,2-diketone π system, respectively. At elevated temperature, styrene is released from the [1+2]-addition product leading to the thermodynamically favored housane species after [2+2] cycloaddition of styrene and c-Si₃ Tip₄ .