NHC-coordinated silagermenylidene functionalized in allylic position and its behaviour as a ligand.

Vinylidenes are common in transition metal chemistry with catalytic applications in alkene and alkyne metathesis. We report here the isolation of a heavier analogue of vinylidene, an α-chlorosilyl functionalized silagermenylidene stabilized by an N-heterocyclic carbene (NHC). Silagermenylidene (Tip2Cl)Si-(Tip)Si=Ge·NHC(iPr2Me2) (4-E/Z; Tip = 2,4,6-(i)Pr3C6H2; NHC(iPr2Me2) = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is available as an E/Z-equilibrium mixture from Tip2Si=Si(Tip)Li and NHC(iPr2Me2)·GeCl2. Reaction of 4-E/Z with Fe2(CO)9 affords a silagermenylidene Fe(CO)4 complex, which slowly isomerizes to its E-isomer at 25 °C. A rearranged Fe(CO)3 complex with an allylic SiGeSi ligand is obtained as a side product at 65 °C.