3,7,10-Trichalcogenaoctasila[3.3.3]propellanes

Article abstract of DOI:10.1002/1099-0682(200112)2001:12<3107::AID-EJIC3107>3.0.CO;2-E

The reaction of hexakis(trimethylsilyl)disilane with acetyl chloride and aluminum chloride yields hexakis(chlorodimethylsilyl)disilane (5a) under carefully controlled reaction conditions. Treatment of 5a with either H₂S/NEt₃ or Li₂E (E = Se, Te) gives the dodecamethyl-3,7,10-trichalcogenaoctasila[3.3.3]propellanes Si₂(SiMe₂)₆E₃ (6a E = S, 6b E = Se, 6c E = Te). The products have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ⁷⁷Se, ¹²⁵Te). The central silicon atoms are very deshielded in comparison with other compounds containing an Si(Si)₄ unit due to their incorporation into three five-membered rings. The molecular structures of 5a and 6a are reported revealing an elongated central Si-Si bond in 5a of 2.3865(11) A and three different spatial orientations of the SiMe₂Cl groups in each Si(SiMe₂Cl)₃ unit. In 6a all three five-membered rings Si₄S adopt envelope conformations with the four silicon atoms in one plane. A view of the Si₈S₃ skeleton along the central silicon-silicon bond of 6a resembles a three-blade propeller.