1-arsa-3-germaallene Tip(t-Bu)Ge═C═AsMes*: the heaviest mixed group 14 and 15 heteroallenic compound.

The 1-arsa-3-germaallene Tip(t-Bu)Ge═C═AsMes* (1, Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl), a stable heavier group 14 and 15 congener of allenes, has been synthesized by debromofluorination of Tip(t-Bu)Ge(F)-C(Br)═AsMes*. It reacts with methanol and 2,3-dimethyl-1,3-butadiene by the Ge═C double bond. The allenic-type structure of 1, featuring cumulated Ge═C and C═As double bonds, has been evidenced by means of spectroscopic and single-crystal X-ray determination. The electronic properties involved in this new system were obtained from DFT calculations. The mechanism of the reaction between 1 and the dimethylbutadiene is also described to understand the observed regio- and chemoselectivity.