Bis(germavinylidene) [(Me3SiN=PPh2)2C=Ge→Ge=C(Ph2P=NSiMe3)] and 1,3-Dimetallacyclobutanes [M{μ2-C(Ph2P=NSiMe3)2}]2 (M=Sn, Pb)

Low-valent metallavinylidenes :M=C/\ are scarce owing to the low stability of such species. Compound 1, prepared from [CH(Ph2P=NSiMe3)2Li(thf)] and GeCl2⋅dioxane, represents the first stable bis(germavinylidene). The dimetallacyclobutanes 2 (M=Pb, Sn) were also prepared—they are believed to form by dimerization of the intermediate metallavinylidenes.