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 Fe2(CO)9 with GeCl2·NHCiPr2Me2 (NHCiPr2Me2 = 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.