The Reaction of Transient 1,1-Bis(trimethylsilyl)silenes with Tris(trimethylsilyl)silyllithium - Synthesis and Structure of Sterically Congested 1-Trimethylsilylalkylpolysilanes

Abstract

Tris(trimethylsilyl)silyllithium (3) reacted with aldehydes and ketones (molar ratio 2 : 1) according to a modified Peterson mechanism under formation of transient silenes, which were immediately trapped by excess 3 to give the organolithium derivatives (Me3Si)3SiSi(SiMe3)2C(Li)R1R2 (7). Hydrolysis of 7 afforded the alkylpolysilanes (Me3Si)3SiSi(SiMe3)2CHR1R2 (8). Depending on the substituents R1 and R2, 7 proved to be rather unstable in THF solution and underwent a rapid rearrangement, involving a 1,3‐Si,C‐trimethylsilyl migration, resulting in the formation of the lithium silanides (Me3Si)2Si(Li)Si(SiMe3)2C(SiMe3)R1R2 (9), which were hydrolized during the aqueous workup to give the H‐silanes (Me3Si)2Si(H)Si(SiMe3)2C(SiMe3)R1R2 (10). Reaction of 9 with chlorotrimethylsilane produced the 1‐trimethylsilylalkylpolysilanes (Me3Si)3SiSi(SiMe3)2C(SiMe3)R1R2 (11). The structures of the products described were elucidated by comprehensive spectral analyses. The results of X‐ray crystal structure analyses, performed for 8 l (R1 = H, R2 = 2,4,6‐(MeO)3C6H2), 10 d (R1 = H, R2 = Mes) and 11 d (R1 = H, R2 = Mes) are discussed and confirm the expected extreme sterical congestion of the molecules.