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