Synthesis and Molecular Structure of Silylated Ethenes and Acetylenes

Abstract Disilylacetylene (1) has been obtained from LiAlH4 reduction of bis(trichlorosilyl)acetylene (2) and bis[(trifluoromethylsulfonyloxy)silyl]acetylene (4). The catalytic hydrosilylation of 2 with HSiCl3 affords tris(trichlorosilyl)ethene (5) and 1.1.2-tris(trichlorosilyl)ethane (6). The synthesis of 6, trans-bis(trichlorosilyl)ethene (8) and 1,1-bis(trichlorosilyl)ethene (9) has been accomplished by hydrosilyiation of trichlorosilylacetylene (7) which was synthesized by the reaction of trichloro(trifluoromethylsulfonyloxy)silane with sodium acetylide. Reductive elimination of halogen from 1,1,1,2-tetrachloro-bis(trichlorosilyl)ethane (10) and 1,2- dibromo-1,1-bis(trichlorosiIyl)ethane (13) gave the corresponding ethenes 1,1-dichloro-bis- (trichlorosilyl)ethene (11), trichloro-trichlorosilylethene (12), 1,1-bis(trichlorosilyl)ethene (9) and 1-chloro-2,2-bis(trichlorosilyl)ethene (14). Tetrakis(trichlorosilyl)ethene (15) has been obtained in a three step synthesis starting from chloromethyl-trichlorosilane or dichloro- methyl-trichlorosilane. By LiAlH4 reduction of trichlorosilylethenes under various reaction conditions, the silylethenes trans-dichloro-di(silyl)ethene (16), 1,1-dichloro-di(silyl)ethene (17), trichloro-silylethene (18), 1-bromo-l-silylethene (19), trans-di(silyl)ethene (20), 1-chloro-2,2-di(silyl)ethene (21), tri(silyl)ethene (22) and 1,1,2-tri(silyl)ethane (23) could be generated. Silylethyne and silyl-chloroethyne were identified as side products. The crystal and molecular structures of 2,5 and 15 have been determined by single crystal X-ray diffraction. 2 and 5 crystallize from the melt in the monoclinic space groups Cc and P21/n, respectively. 15 has been crystallized by sublimation (orthorhombic. space group Pbca). 5 and 15 feature strongly distorted ethene skeletons with a double bond twist of 28.1° in 15.