The first germaphosphaallene, 3, has been obtained by debromofluorination of the (fluorogermyl)bromophosphaalkene 7 and characterized by 31P NMR (240 ppm) and 13C NMR (280.9 ppm for the allenic carbon) at low temperature. Methanol and methyllithium react exclusively with the GeC double bond to afford the corresponding adducts 9 and 10. In the absence of a trapping reagent, 3 gives two types of dimer, 13a (involving two GeC bonds) and 14a (involving one GeC and one PC bond).

The first arsaphosphaallene, ArPCAsAr (1; Ar = 2,4,6-tri-tert-butylphenyl), has been synthesized by debromofluorination of the (phosphaalkenyl)fluoroarsane 5 by n-butyllithium at low temperature and characterized by NMR (δP +159.7 ppm, δC +299.5 ppm) and X-ray analysis. A 1H NMR study between +55 and −60 °C allowed the determination of the rotation barrier of Ar groups.