3,7,10-trichalcogenaoctasila[3.3.3]propellanes

The reaction of hexakis(trimethylsilyl)disilane with acetyl chloride and al uminum chloride yields hexakis(chlorodimethylsilyl)disilane (5a) under care fully 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 Si-2(SiMe2)(6)E-3 (6a E = S, 6b E = Se, 6c E = Te). The pro ducts have been characterized by multinuclear NMR spectroscopy (H-1, C-13, Si-29, Se-77, Te-125). The central silicon atoms are very deshielded in com parison with other compounds containing an Si(Si)(4) unit due to their inco rporation into three five-membered rings. The molecular structures of 5a an d 6a are reported revealing an elongated central Si-Si bond in 5a of 2.3865 (11) Angstrom and three different spatial orientations of the SiMe2Cl group s in each Si(SiMe2Cl)(3) unit. In 6a all three five-membered rings Si4S ado pt envelope conformations with the four silicon atoms in one plane. A view of the Si8S3 skeleton along the central silicon-silicon bond of 6a resemble s a three-blade propeller.