A Molecular Complex with a Formally Neutral Iron Germanide Motif (Fe2Ge2)

We report the synthesis and isolation of a stable complex containing the formally neutral Fe2Ge2 motif, which IS stabilized by the coordination of an N-heterocyclic carbene to the germanium and of carbon monoxide to the iron center. [(NHCiPr2Me2)GeFe(CO)(4)](2) is obtained by reduction of the -NHCiPr2Me2-coordinated dichlorogermylene adduct of Fe(CO)(4), which in turn is obtained from the reaction of Fe-2(CO)(9) with GeCl2 center dot NHCiP2Me2 (NHCiPr2Me2 = 1,3-diisopropyl-4,5-amethylimidazol-2-ylidene). The solid-state structure of the title compound reveals two distinct coordination modes for the Fe(CO)(4) fragments: bridging (pi-type) and terminal (sigma-type). In solution, the rapid equilibrium between the two modes was resolved by NMR at -35 degrees C. Reaction with propylene sulfide at room temperature affords the sulfide-bridged digermanium complex with two terminal Fe(CO)(4) moieties.