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

The reactions of the trichlorodisilanes ClRMeSi-SiMeCl2 (R = Me, Ph) with e ither H2S/NEt3 or Li2E (E = Se, Te) result in the selective formation of 2, 5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)(2)E-3 (R = Me, P h/E = S, Se, Te). In the cases of R = Ph, three stereoisomers with differen t spatial orientations of the phenyl substituents arise. The isomers with b oth phenyl substituents in equatorial positions are formed preferably. All products have been characterized by multinuclear NMR spectroscopy including (1)J(SiSe) and (1)J(SiTe) coupling constants. A crystal structure analysis of the isomer of (PhMeSiSiMe)(2)S-3 with both phenyl substituents in equat orial positions reveals a very small bond angle at the bridging sulfur atom of 88.5 degrees which is even 4.6 degrees smaller than in the parent norbo rnane C7H12. (C) 2001 Elsevier Science B.V. All rights reserved.