In summary, we investigated the reactivity of permercurated ferrocene derivatives towards neutral ligands in standard organic solvents as well as in superacidic medium. We demonstrated that in the compound FeC10(HgTFA)10 all mercury atoms are accessible to Lewis bases. The Lewis acidity of the {FeC10Hg10} 10+ framework was tuned by variation of the counter anions. While the TFA salt only binds to strong σ-donors like dmap, the presence of weakly coordination anions allows to isolate solvent adducts [FeC10(HgL 2b (middle) and 2c (top) in acetonitrile without supporting electrolyte at 100mV/s scan rate and room temperature.