A Phosphanyl Phosphagermene and its Reactivity

Reaction of a nucleophilic germylene Ge[CH(SiMe₃)₂]₂ with the phosphanyl phosphaketene [{(H₂C)(NDipp)}₂P]PCO induces decarbonylation to form a phosphanyl phosphagermene [{(H₂C)(NDipp)}₂P]P=Ge[CH(SiMe₃)₂]₂ (1; Dipp=2,6-diisopropyl-phenyl). Addition of CO₂ or MeCN to 1 results in [3+2]-cycloaddition reactions to afford five-membered heterocycles. This mode of reactivity is reminiscent of that observed for frustrated Lewis pairs, with the pendant phosphanyl group acting as a base and the germanium center as a Lewis acid. Contrastingly, 1,2-addition across the P=Ge bond was observed when using ammonia, small primary amines (NH₂ ⁿP), or metal complexes (e. g. Au(PPh₃)Cl and ZnEt₂). These latter reactions allow for the one-step synthesis of metal phosphide complexes.