SYNTHESIS AND STRUCTURE OF METHOXYBIS[TRIS(TRIMETHYLSILYL)SILYL]METHANE - THE FIRST GEMINAL DI(HYPERSILYL) COMPOUND WITH A CENTRAL CARBON-ATOM

Methoxy-bis[tris(trimethylsilyl)silyl]methane (4), the first compound bearing two hypersilyl groups at a carbon atom, was synthesized by the reaction of tris (trimethylsilyl) silyllithium with dichloromethyl me thyl ether. As a byproduct of the reaction, 1,2-dimethoxy-1,2-bis[tris (trimethylsilyl)silyl]- ethane (5) could be identified. Possible pathw ays leading to 4 and 5 are discussed. The structure of 4, elucidated b y an Xray crystal structure analysis, is characterized by tremendous d istortions of the molecular skeleton due to the spatial demand of the two extended hemispherical (Me(3)Si)(3)Si groups. For example, the cen tral Si-C-Si angle is widened to 132.7 degrees, the trimethylsilyl gro ups of the two hypersilyl substituents are pressed together to give an average Si-Si-Si angle of 105.6 degrees, and the methoxy carbon atom and the nearest neighboring trimethylsilyl carbon atom approach to a d istance of 3.25 Angstrom, i.e, approx. 19% less than the sum of the va n der Waals radii of two methyl groups.