A Ferrocene‐Based Dicationic Iron(IV) Carbonyl Complex

The 16‐valence electron species [Cp*2Fe]2+ (Cp*=η‐C5Me5), formally featuring a tetravalent iron ion, quantitatively binds CO in HF solution to form the stable, diamagnetic carbonyl species [Cp*2Fe(CO)]2+. This dication forms salts in the presence of AsF6− and SbF6− that were crystallographically characterized. The molecular structure in crystals of [Cp*2Fe(CO)](AsF6)2 displays cyclopentadienyl rings that are clearly not parallel and an equatorially bound η1‐CO ligand. The formal oxidation state +IV of iron was investigated by 57Fe Mössbauer spectroscopy and is supported by DFT computational analysis. A detailed spectroscopic characterization of the hitherto unprecedented high‐valent iron carbonyl compounds is reported.