(1,1′-Ferrocenediyl)dimethylsilane: An Electroactive Monolayer Derivatizing Reagent. Characterization of Surface-Oxygen-(Dimethylsilyl)ferrocene by Cyclic Voltammetry and Solid-State Nuclear Magnetic Resonance

(1,1′-Ferrocenediyl)dimethylsilane (I) has been used to functionalize the surfaces of smooth Au, smooth Pt, single-crystal n-type (100) Si, (111) Si, and (111) Ge, textured (100) Si, and rough (111) Ge electrodes. For the smooth surfaces the coverage of electroactive material is between 3.5 × 10⁻¹⁰ and 4.9 × 10⁻¹⁰ mol/cm² for a large number of independent preparations. This coverage is consistent with an approximate monolayer of the ferrocene. The textured and rough surfaces give larger coverages consistent with an increase in the effective coverage by a factor of ∼2–5. The E°′ for the surface-confined ferrocene in CH₃CN/0.1 M (n-Bu₄N)C10₄ on Pt or Au is + 0.43 V vs. SCE. The full width of cyclic voltammetry waves at half-height on Pt and Au is ∼210 mV, consistent with nonideality in surface activities. Solid-state cross-polarization/magic-angle spinning, natural abundance, ²⁹Si, and ¹³C NMR of high surface area silica (400 m²/g) bearing ∼10^−u mol/cm² of ferrocene-centered material confirms the mode of attachment of I to be surface-O-(dimethylsilyl)ferrocene. The ²⁹Si NMR shows a single resonance due to surface-anchored material at ∼ +7 ppm (relative to tetramethylsilane) consistent with the -O-SiMe₂Fc structure (Fc = ferrocenyl) and the ¹³C NMR shows a singlet at ∼0 ppm (relative to tetramethylsilane) for the methyl carbons and an unresolved multiplet at ∼ +69 ppm (relative to tetramethylsilane) for the nonequivalent cyclopentadienyl carbons.