Disilene anion radical

The ESR parameters of disilene anion radicals 154-160 are summarized in Table VIII. The hyperfine coupling constants (hfscs) for the unsaturated silicons [a(Sio,)]... 

ESR Parameters of Disilene Anion Radicals and Related Radicals... 

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... 

Scheme 6.12.1 Synthesis of Disilene Anion Radical [LithiumltetrahydrofuranM Tetrakis(di-tbutylmethylsilyl) disilene Anion Radical.

The masked disilene monomers 1-5 were prepared by reaction of dichlorodisilanes of the type ClSiR1R2SiMe2Cl with the biphenyl anion radical as described before. These are composed of two regio isomers, a and b, the predominant isomer being a, as determined by H NMR NOE difference spectra. 

After review OW, the molecular structures in the solid state of 13 acyclic di-silenes, 13 endo- and exocyclic disilenes, 4 silicon-based dienes, 6 disilenes with radical, cation, and anion center, and one disilyne have been determined by X-ray analysis. Although the structural characteristics of a number of these new disilenes are summarized in a recent review by Weidenbruch,9 the structural parameters of all new disilenes reported after review OW are listed in Tables I-IV. 

A. Sekiguchi, S. Inoue, M. Ichinoche and Y. Arai, Isolable anion radical of blue disilene (,Bu2MeSi)2Si=Si(SiMeiBu2)2 formed upon one-electron reduction synthesis and characterization. J. Am. Chem. Soc. 126, 9626-29 (2004). 

Reduction of tetrakis(trialkylsilyl) disilene with Li in THF or K in DME gives the corresponding 1,2-dianions, together with the anion radicals [Eq. (31)1 (72). 

To overcome this stability problem, the high reactivity of disilenes can temporarily be masked by adding a suitable auxiliary group. Roark and Peddle found that an adduct can be formed from dichlorodisilane and a biphenyl anion radical yielding the masked disilene (Fig. 7) [33]. 

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). 

Scheme 7.1.3 Redox Behavior of Disilene Generating Cation Radical and the Anion Radical.

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