Disilene anion radical lithium

Disilene Anion Radical [Lithium(tetrahydrofuran)4]+Tetrakis(di- butylmethylsilyl)disilene Anion Radical 33... 

Preparation of [lithium(tetrahydrofuran)4f tetrakisidi-tbutylmethylsilyl) disilene anion radical 33 References 34... 

Tetrakis di-fbutylmethylsilyl)disilene has proved to be a versatile precursor for the isolation of remarkable radical species (6,7). The disilene bearing four fBu2MeSi groups can be successfully synthesized by two routes (7). The treatment of tetrakis di-fbutyl-methylsilyl)disilene with 2.2 equiv of lithium naphthalenide in THF at — 78°C afforded the silylene anion radical in 56% yield. The reaction rnkture was first slowly warmed to room temperature. The dark blue color of disilene completely disappeared and a red solution was produced during the reaction. The eventual addition of 4.3 equiv of 12-crown-4 to the resulting reaction mixture led to the isolation of the silylene anion radical as air-and moisture-sensitive red crystals (8). 

A lithium naphthalenide solution can be prepared by stirring equimolar quantities of naphthalene and lithium in THF. This solution of lithium naphthalenide (0.34 mmol) in THF was added to tetrakis di-fbutylmethylsilyl)disilene (112 mg, 0.16 mmol) in THF 2.5 mL) at -78°C with the help of a syringe. Afterward the reaction mixture was allowed to warm up to room temperature over 2 h. There was a rapid color change resulting in the formation of the 1,2-dianion of the disilene (6). This dianion was further treated with 12-crown-4 (110 irL, 0.69 mmol, 4.3 equiv) at room temperature. Afterward THF was removed in vacuo and hexane was added to the reaction mixture. The hexane solution was filtered and overnight standing at -30°C led to the isolation of silylene anion radical as air- and moisture-sensitive red crystals (128 mg, 56%). Mp 138-139°C (Scheme 6.1.1.1). 

Removal of halogen from a vicinal dihalide with zinc can be used to form olefins, although it is not a common method for alkene synthesis. Similarly, dehalogenation of >SiX-SiX< with alkali metals appears to be successful in a limited sense. When R2Si(X)Si(X)R2 (R = t-Bu X = C1, Br) or RR Si(Cl)Si(Cl)RR (R = t-Bu R = c-C6H,) are reacted with lithium (sodium or potassium), the radical anion of the disilene is formed which is particularly long-lived in the latter case181. However, several intermediate... 

The reduction of l,2-di-terf-butyl-l,2-dicyclohexyl-l,2-dichlorodisilane with excess lithium yields the radical anion of l,2-di-tert-butyl-l,2-dicyclohexyldisilene (g = 2.0033, flSi=49.8 G), with equivalent silicon atoms and a half-life of about 12 h49. The intermediacy of the disilene in the reduction process was supported by a trapping experiment with anthracene. The ESR spectrum of the less severely hindered tetracyclohexyldisilene radical anion was not observed under otherwise identical conditions. 

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