Synthesis and characterization of 2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)2E3 (R=Me, Ph/E=S, Se, Te)

The reactions of the trichlorodisilanes ClRMeSi–SiMeCl2 (R=Me, Ph) with either H2S/NEt3 or Li2E (E=Se, Te) result in the selective formation of 2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)2E3 (R=Me, Ph/E=S, Se, Te). In the cases of R=Ph, three stereoisomers with different spatial orientations of the phenyl substituents arise. The isomers with both phenyl substituents in equatorial positions are formed preferably. All products have been characterized by multinuclear NMR spectroscopy including 1JSiSe and 1JSiTe coupling constants. A crystal structure analysis of the isomer of (PhMeSiSiMe)2S3 with both phenyl substituents in equatorial positions reveals a very small bond angle at the bridging sulfur atom of 88.5° which is even 4.6° smaller than in the parent norbornane C7H12.