Tris(lithiomethyl)silanes, RSi(CH2Li)3, and tetrakis(lithiomethyl)silane, Si(CH2Li)4, were
prepared by the reductive C−S bond cleavage with lithium p,p‘-di-tert-butylbiphenylide
(LiDBB) and characterized by trapping with Bu3SnCl. The yields of the isolated trapping
products were 42−81% (>95% NMR yield of the crude product), indicating a high-yield
synthesis of the corresponding poly(lithiomethyl)silane building blocks. Tetrakis(lithiomethyl)silane is the first compound containing four lithioalkyl groups without any stabilization
of the metalated carbon atoms by π-systems. Tetrakis(lithiomethyl)silane was used for the
synthesis of 2,2,3,3,7,7,8,8-octamethyl-2,3,5,7,8-pentasilaspiro[4,6]nonane (10), a new spirocyclic disilane. The single-crystal X-ray diffraction study of 10 indicates two five-membered
rings in envelope conformation with ecliptically arranged methyl groups connected to a spiro
compound by a central silicon atom. DFT geometry optimizations [B3LYP/6-31G(d) level]
and NMR calculations (GIAO method, HF/6-31+G(d,p) level) of 10 confirm the observed
conformation of 10 as an energetic minimum and support the experimental results.
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