The mono- and di-cations of decamethylbiferrocene (1) have been obtained as triiodide salts by oxidation of decamethylbiferrocene with I2 in THF. The X-ray crystal structure of [1](I3) at 295 K and the Mössbauer data show a localized mixed-valence system. The salt [1] (I3)2 has a single Mössbauer quadrupole doublet at 4.5 K with FeIII parameters (IS = 0.537 mm s-1 vs. Fe; QS = 0.237 mm s-1) with small antiferromagnetic coupling (θ = -5.58 K). © 1993.