Studies Toward Persilylation of π-Cyclopentadienyl Complexes of Fe and Ru. Molecular Structures of [Fe(C5H5){C5(SiMe2H)5}], [Fe(C5H5){C5Br3(SiMe3)2}] and [Fe(C5H5){C5Br2(SiMe3)3}]

Increasing the number of SiMe3 substituents on a cyclopentadienyl ring has, in addition to a stabilizing effect of unusual coordination geometries and oxidation states, the effect of increasing the solubility in unpolar solvents and increasing the volatility. Starting from pentabromoferrocene and pentabromo(pentamethyl)ruthenocene, we could achieve the introduction of up to five silyl (SiMe2H or SiMe3) groups to give [Fe(C5H5){C5(SiMe2R)5}], R = H, Me, and [Ru(C5Me5){C5(SiMe2H)5}]. However, yields were very low, and nearly all intermediate steps afforded mixtures of similar silyl-substituted compounds, which were difficult to separate. The crystal structures of [Fe(C5H5){C5(SiMe2H)5}] (13a), [Fe(C5H5){C5Br3(SiMe3)2}] (4b), and [Fe(C5H5){C5Br2(SiMe3)3}] (8b) were determined.