Bis(trimethylsilyl) sulfide

Synthesis

Bis(trimethylsilyl)sulfide can be prepared in one step from Li₂S and TMS chloride. The specific steps are as follows: TMS chloride (50.8 mL, 0.40 mol) is added to a magnetically stirred suspension of anhydrous Li₂S (9.19 g, 0.20 mol) in anhydrous THF (40 mL). The mixture is stirred under dry argon for 25 hours. GC analysis of aliquots of the supernatant at this time shows bis(trimethylsilyl)sulfide (87%), siloxane (4.1%), and unreacted TMS chloride (9.2%). A small Vigreaux column with a vacuum jacket is fitted to the reaction flask, and THF is removed by distillation under argon. The pressure is then reduced, and after a short pre-distillation, the bis(trimethylsilyl)sulfide is collected as a clear, colorless liquid (29.7 g, 83%).

Chemical Properties

clear colorless to slightly yellow liquid

Physical properties

bp 164°C; d 0.846 g cm3.

Uses

Hexamethyldisilathiane may be used in the bis-O-demethylation of dimethoxy aromatic compounds.
It may also be used as a sulfur source in the following conversion:

• Amides and lactams to their corresponding sulfur analogs.
• Allyl alcohols to diallyl sulfides.
• Transition metal halides to metal sulfides.
• Aryl iodides to diaryl sulfides.

Uses

Bis(trimethylsilyl) sulfide (TMS2S) is used to reduce aromatic nitro groups to amines and the oxides of sulfur, selenium, and tellurium. Conditions for nitro group reduction (eq 1) are forcing; however, yields are good. Reactions of TMS2S with primary aliphatic nitro groups result in the formation of the thiohydroxamic acids (eq 2) which can be isolated or carried further to the nitrile. Secondary alkyl nitro derivatives provide oximes. Sulfoxides are reduced to sulfides, selenoxides to selenides, and telluroxides to tellurides. Conditions are mild and work well on both the aliphatic and aromatic oxides.

Uses

Bis(trimethylsilyl)sulfide is used as a silylating agent in the synthesis of pseudohalides, trifluoroacetate and tetramethylsilyl halides. It is used in the transformation of oxides and chlorides into corresponding sulfides. It is also used in the preparation of dimethyltrisulfane as well as thiones from aldehydes and ketones. Further, it is used as a reducing agent to reduce aromatic nitro compounds to amines.

Purification Methods

Dissolve it in pet ether (b ca 40o), remove the solvent and distil it. Redistil it under atmospheric pressure of dry N2. It is collected as a colourless liquid which solidifies to a white solid in Dry-ice. On standing for several days it turns yellow possibly due to liberation of sulfur. Store it below 4o under dry N2. [Eaborn J Chem Soc 3077 1950, Beilstein 4 IV 4033.]