Mixtures of polysilylated metallocenes FeC10DMSnH10-n (n = 10, 9, 8, 7) were successfully separated by HPLC allowing a systematic study on silylation effects on ferrocene by XRD, CV, NMR and UV/VIS spectroscopy. Herein, the steric overcrowding is reflected by significant rotational hindrance of the tetraand pentasilylated cyclopentadienyl ligands regarding the DMS groups and greater ordering. Furthermore, the cyclopentadienyl ligands are found to exhibit distortions from planarity within the molecular structure. The maximum UV/vis absorbances are systematically red-shifted with further silylation indicating decreased energy gaps between occupied and virtual MOs. DFT calculations show that this is largely due to the lengthening of the Fe-C bonds caused by the steric crowding induced by the silyl substituents. The occupied frontier MOs are largely nonbonding in nature and thus not affected much by the substitution, in agreement with small changes in the redox potentials. But the metal-ligand antibonding character of the lowest-lying virtual MOs is reduced compared to the parent ferrocene, giving rise to the observed red shifts.