Arsaalkyne

In chemistry, a arsaalkyne (IUPAC name: alkylidynearsane) is an organoarsenic compound containing a triple bond between arsenic and carbon with the general chemical formula R−C≡As. Arsaalkynes are rare, especially in comparison with the phosphaalkynes. The parent H−C≡As has been characterized spectroscopically, otherwise the only arsaalkynes have bulky organic substituents.^[1]

Chemical structure of the arsaalkyne As≡C−C₆H₂-2,4,6-(t-Bu)₃.

Synthesis and isolation

Arsaalkynes are produced by dehydrohalogenation or related base-induced elimination reactions. The case of HCAs is illustrative:

Cl−CH₂−AsH₂ + 2 Na₂CO₃ → H−C≡As + 2 NaHCO₃ + 2 NaCl

Owing to the principles of the double bond rule, arsaalkynes tend to oligomerize more readily than the phosphorus analogues. Thus attempts to prepare Me₃C−C≡As produce the tetramer, which has a cubane structure.^[2] The very bulky substituent −C₆H₂-2,4,6-(t-Bu)₃ does however allow the crystallization of the monomeric arsaalkyne. Its As-C bond length is 1.657(7) Å.^[3]

See also

• Cyaarside