The persilylated derivative is only poorly soluble in most organic solvents but can consequently be easily separated by crystallization from THF or n-pentane to afford compound 6 as a purple solid. Further purification of the remaining polysilylated metallocene mixtures was accomplished by reverse phase HPLC, using methanol/water as eluent. Starting from the crude mixture not only the hepta-, octa-, nona-and decakis(dimethylsilyl)ferrocene were separated, but also their corresponding regioisomers in milligram scale. Considering the heptakis-and octakis(dimethylsilyl)ferrocene, in principle four or three possible regioisomers, respectively, exist. However, only four of seven possible compounds were isolated. The distribution of the observed substitutional pattern reveals that silylation occurs equally at both Cp ligands rather than a consecutive silylation of only one Cp ligand, as metallocenes 3c, 3d and 4c with a tetrakis(dimethylsilyl)cyclopentadienyl ligand were dominantly formed (Figure , purple). This indicates that the silylation may be hampered due to strong sterical hindrance.