Arsenic Ylides and Pentaalkylarsoranes

Only one alkylidene trialkylarsorane has been prepared in a pure state and fully characterized (73). This compound, (CH3)3AsCH2, can be obtained through desilylation of a trimethylsilyl precursor (34) (first synthe- 

Methylene trimethylarsorane (the term trimethylarsonium methylide is equally correct) had already been formulated in 1953 by Wittig and Torssell (104) who studied the reaction of tetramethylarsonium salts with organolithium compounds. Although this method cannot be used for the preparation of the salt-free material due to the strong complexation by the lithium cations, it is clear from reactions of the product mixture that the ylide is present in solution. The formation of arsonium salts upon addition of alkyl halides is a typical example  

At room temperature, methylene trimethylarsorane (73) is a colorless crystalline compound, mp 33°C, which sublimes in a vacuum at 20°C/0.1 mm Hg. It is rapidly decomposed above 33°C trimethylarsine and polymethylene are the main products formed. Blue and brown colors develop and some gas is evolved, predominantly ethylene. With trimethylphos-phine, a methylene transfer reaction takes place yielding trimethylarsine and methylene trimethylphosphorane  

The compound is extremely sensitive to oxygen and moisture and must be handled with great care. 

Thick fumes are observed when the material is exposed to air and spontaneous ignition may occur. A vigorous reaction with water leads to a strongly alkaline solution of some tetramethylarsonium hydroxide, but trimethylarsenic oxide is also formed (104)- Tetramethyl methoxyarsorane can be obtained in a quantitative yield (68) with methanol under carefully 

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