Tetrasubstituted Selenophenes from the Stepwise Assembly of Molecular Fragments on a Diiron Frame and Final Cleavage of a Bridging Alkylidene.

A series of 2,3-dicarboxylato-5-acetyl-4-aminoselenophenes, -, was obtained via the uncommon assembly of building blocks on a diiron platform, starting from commercial [FeCp(CO)] through the stepwise formation of diiron complexes [-]CFSO, -, and -. The selenophene-substituted bridging alkylidene ligand in - is removed from coordination upon treatment with water in air under mild conditions (ambient temperature in most cases), affording - in good to excellent yields. This process is highly selective and is accompanied by the disruption of the organometallic scaffold: cyclopentadiene (CpH) and lepidocrocite (γ-FeO(OH)) were identified by NMR and Raman analyses at the end of one representative reaction. The straightforward cleavage of the linkage between a bridging Fischer alkylidene and two (or more) metal centers, as observed here, is an unprecedented reaction in organometallic chemistry: in the present case, the carbene function is converted to a ketone which is incorporated into the organic product. DFT calculations and electrochemical experiments were carried out to give insight into the release of the selenophene-alkylidene ligand. Compounds - were fully characterized by elemental analysis, mass spectrometry, IR, and multinuclear NMR spectroscopy and by X-ray diffraction and cyclic voltammetry in one case.