"Inverse Sandwich" Complexes of Perhalogenated Cyclohexasilane

Perhalogenated cyclohexasilanes, Si6X12 (X = Cl, Br), were prepared by reaction of Si6H12 with molecular chlorine or bromine in cold (−89 °C) dichloromethane. Single-crystal structural determination by X-ray analysis shows that the six silicon atoms comprising Si6Br12 adopt a chair conformation in the solid state. The addition of p-tolunitrile to Si6X12 (X = Cl, Br) leads to the rapid formation of colorless precipitates. Si6Br12·2(p-CH3C6H4CN) adopts an “inverse sandwich” structure where the N atoms of the p-tolunitrile molecules are μ6 bonded and are located above and below the planar hexagonal Si6 ring.