Organic Syntheses, CV 5, 1016
TETRAMETHYLBIPHOSPHINE DISULFIDE
[Diphosphine, tetramethyl-, disulfide]
Submitted by G. W. Parshall
1
Checked by W. S. Wadsworth and William D. Emmons.
1. Procedure
A
3-l. round-bottomed flask equipped with
mechanical stirrer,
condenser (surmounted by a drying tube),
thermometer, and
addition funnel is charged with
800 ml. of 3M methylmagnesium bromide solution (2.4 moles) (Note
1) and
600 ml. of anhydrous ether. The solution is stirred and cooled to 0–5° while a solution of
135 g. (83 ml., 0.80 mole) of thiophosphoryl chloride (Note
2) in
85 ml. of ether is added over a period of 3 hours. A thick white precipitate forms during the course of the addition. After completion of the addition, the reaction mixture is poured onto 500 g. of ice in a
4-l. beaker.
Sulfuric acid (900 ml. of 10% solution) is added over a period of 20 minutes with gentle stirring. The mixture is filtered, and the white solid product is washed with 4 l. of water and recrystallized from
2 l. of ethanol. The product is dried over
phosphorus pentoxide in a
vacuum desiccator to give
50–55 g. (
67–74%) of white crystalline
tetramethylbiphosphine disulfide, m.p.
223–227° (Note
3). Evaporation of the mother liquor to a volume of 900 ml. gives an additional
3 g. of
tetramethylbiphosphine disulfide, m.p.
222–225°.
2. Notes
3.
Tetramethylbiphosphine disulfide melts sharply at
227° when pure, but the material obtained as described above is satisfactory for most reactions.
3. Discussion
4. Merits of the Preparation
Tetramethylbiphosphine disulfide is an extremely versatile intermediate for the preparation of compounds containing two methyl groups on
phosphorus, for example,
dimethylphosphine.
5 Most other methods for the preparation of such compounds give large amounts of mono- and trimethylated by-products.
Tetramethylbiphosphine disulfide has been converted in high yields to
dimethylphosphinic acid,
3,4 dimethylphosphinyl chloride,
4,6 dimethylchlorophosphine,
7 and
dimethylthiophosphinic bromide.
8 Other tetraalkylbiphosphine disulfides have been converted to tetraalkylbiphosphines, dialkylthiophosphoryl bromides, and dialkylphosphinic anhydrides.
9 Addition of
tetramethylbiphosphine disulfide to
ethylene followed by desulfurization gives
tetramethylethylenediphosphine, a powerful chelating agent.
10 Other alkyl Grignard reagents also react with
thiophosphoryl chloride under the conditions of the present procedure to give the corresponding tetraalkylbiphosphine disulfides in high yield.
5,11
This preparation is referenced from:
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