Synthesis and Characterization of Bidentate Isonitrile Iron Complexes

The divalent iron complexes trans-[FeBr2(BINC)2], [Cp*FeCl­(BINC)] (Cp* = Me5C5), and [FeBr2(CNAr3NC)2] with the chelating bis­(isonitrile) ligands BINC (bis­(2-isocyanophenyl)­phenylphosphonate) and CNAr3NC (2,2″-diisocyano-3,5,3″,5”tetramethyl-1,1′:3′,1″-terphenyl) have been prepared and characterized. Their subsequent reduction yields the di- and trinuclear compounds [Fe3(BINC)6], [Cp*Fe­(BINC)]2, [Fe­(CNAr3NC)2]2, and [K­(Et2O)]2[Fe­(CNAr3NC)2]2. The molecular structures of all new species were determined by X-ray crystallography and compared to those of related iron carbonyl complexes, demonstrating that the bidentate isonitrile ligands are capable surrogates for two CO ligands with only minimal distortion of the tetrahedral or octahedral geometry of the parent complexes. The complexes were further characterized by NMR and IR spectroscopy, and the electrochemical properties of selected compounds were analyzed by UV–vis–NIR spectroelectrochemistry.