Singe crystals of all isolated compounds were obtained by recrystallization from MeOH/H2O or THF mixtures and analyzed via single-crystal XRD. The steric influence of the polysilylated cyclopentadienyl ligands becomes visible by several features: for the sterically overcrowded metallocenes a staggered conformation is preferred. In the solid state structures extraordinarily large Fe-C bond lengths up to 2.118(1) Å in comparison to unsubstituted ferrocene (Fe-C: 2.051(2) -2.063(2) Å ) are observed, indicating repulsion of the parallel cyclopentadienyl ligands. Furthermore, a bent structure for the cyclopentadienyl ligands is observed, as almost all Si atoms are found out of the Cp plane (Tab. 1, Si-Cp plane ). This effect is most pronounced in the [FeC10DMS10] (6) and [FeC10DMS9H] (5) structures which exhibit even larger angulations in 1,1',2,2',4,4'-hexakis(trimethylsilyl)ferrocene (12.8 °[39] ). Moreover, the DMS groups on the persilylated ligand prefer to order in a highly symmetric circular manner. As a result, two sets of methyl groups are found pointing towards or away from the iron center while the silicon-hydrogen bond is in the same plane as the Cp ligand. In unsymmetrically silylated ferrocenes (e.g., 3a, 4a) the repulsive interaction is compensated by tilting of the respective ferrocene (Tab. 1, Cp-Cp' tilt ), whereon the parallel orientation of the DMS substituents on the less substituted Cp ligands is repealed (Figure ). [a] Multiple metallocene molecules are found within the asymmetric unit.