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. [(NHC^iPr₂Me₂)­GeFe­(CO)₄]₂ is obtained by reduction of the NHC^iPr₂Me₂-coordinated dichlorogermylene adduct of Fe­(CO)₄, which in turn is obtained from the reaction of Fe₂(CO)₉ with GeCl₂·NHC^iPr₂Me₂ (NHC^iPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). The solid-state structure of the title compound reveals two distinct coordination modes for the Fe­(CO)₄ fragments: bridging (π-type) and terminal (σ-type). In solution, the rapid equilibrium between the two modes was resolved by NMR at −35 °C. Reaction with propylene sulfide at room temperature affords the sulfide-bridged digermanium complex with two terminal Fe­(CO)₄ moieties.