Nonsolvated, Aggregated 1,1‐Dilithiosilane and the Derived Silyl Radicals

Abstract

Ein Triplett‐Silyldiradikal 2 und eine Familie von Silylradikalen, in denen das Silylradikalzentrum Teil eines Silyllithiumaggregats ist, entstehen photochemisch aus dem gem‐Dilithiosilan [(R2SiLi2)(R2HSiLi)2] (1, siehe Schema; R′: unbekannt). Das EPR‐Spektrum von 2 besteht aus vier Seitenbanden, die von ΔM=1‐Übergängen herrühren, und einem Signal bei halbem Feld, das von den verbotenen ΔM=2‐Übergängen stammt.

[{(tBu2Me)2Si}3Li4]2−: An Aggregated Dianion of a 1,1‐Dilithiosilane with a Unique Structural Motif

“…The 7 Li chemical shifts of solvated silyllithium compounds are around 0.5 ppm,19 while those of aggregated silyllithium19 and organolithium20 compounds are around 3 ppm. Compound 1 , a coaggregate of mono‐ and dilithium silyl units, has δ ( 7 Li) values of 4.2 and 5.4 ppm 5. The observed δ ( 7 Li) value of 7 ppm in 2 is further downfield and consistent with 2 being an aggregate of dilithiosilane.…”

“…3c Recently, we reported the structure of unsolvated 1 [see Eq. (1)], which has a unique R 2 SiLi 4 core fragment, formed by co‐aggregation of one molecule of R 2 SiLi 2 with two molecules of R 2 SiHLi 5. Also for solvated geminal dilithio organic compounds R 2 CLi 2 1a only limited structural information is available, although they have important synthetic applications 1b.…”

“…When 1 is dissolved in THF two compounds are produced [Eq. (1)]: solvated silyllithium 3 5 and 2 in 6:1 molar ratio. The formation of aggregate 2 in THF is unexpected, because in most previous cases studied addition of THF led to solvated lithiosilanes11 or dilithiosilanes 3c.…”

Ein stabiles Silylenoid und ein Donor‐stabilisiertes Chlorsilylen – niedrig koordinierte Siliciumverbindungen und kein Ende?

“…So ergibt beispielsweise die Einwirkung von Methanol das Silan 11 , während mit Methyllithium die Silyllithium‐Verbindung 12 erhalten wird. Mit Lithium oder tert ‐Butyllithium resultiert das Radikal 13 , das kürzlich auch auf anderem Wege erhalten worden war 12…”

A Stable Silylenoid and a Donor‐Stabilized Chlorosilylene: Low‐Coordinate Silicon Compounds—A Never‐Ending Story?

“…Thus, for example, reaction with methanol furnishes the silane 11 , and the reaction with methyllithium affords the silyl lithium compound 12 . Reactions with lithium or tert ‐butyllithium give rise to the radical 13 , which was recently obtained by a different route 12…”