Unsubstituted ferrocene. One major challenge in converting [FeC10Br10] effectively into the consecutive silylated ferrocene was to avoid trapping of protons by basic intermediates. Therefore, the reaction itself and especially the used solvents and silanes as well as the glassware had to be kept as dry as possible (ESI, S1). The persilylation of [FeC10Br10] was carried out by direct reaction with elemental magnesium or by bromine-lithium exchange followed by subsequent trapping with a suitable DMS electrophile (Scheme 1, bottom). Herein, the degree of silylation was followed by mass spectrometry.