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 alpha-chlorosilyl functionalized silagermenylidene stabilized by an N-heterocyclic carbene (NHC). Silagermenylidene (Tip(2)Cl)-Si(Tip)Si=Ge.NHCiPr2Me2 (4-E/Z; Tip = 2,4,6-(Pr3C6H2)-Pr-i; NHCiPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is available as an E/Z-equilibrium mixture from Tip(2)Si=Si(Tip) Li and NHCiPr(2)Me(2).GeCl2. Reaction of 4-E/Z with Fe-2(CO)(9) affords a silagermenylidene Fe(CO)(4) complex, which slowly isomerizes to its E-isomer at 25 degrees C. A rearranged Fe(CO)(3) complex with an allylic SiGeSi ligand is obtained as a side product at 65 degrees C.