Synthesis and Characterization of Ferrocene Derivatives

All compounds were obtained from SigmaAldrich and used as received unless otherwise indicated. TEMPO was purified by sublimation under vacuum prior to use. Solvents were purchased from Fisher and deuterated solvents were purchased from Cambridge Isotope Labs. Methylene chloride was dried by running through a column of activated alumina, degassed, and stored over 4 Å molecular sieves before use. TEMPOH was synthesized following the literature reported anhydrous synthesis.^{45 (link)} Methanol-D (CH₃OD) was dried over 4 Å molecular sieves and stored under inert atmosphere. Anhydrous TEMPOD was synthesized by stirring TEMPOH with CH₃OD for 1h then removing volatiles under vacuum. Pyridine bases were distilled and dried over 4 Å molecular sieves. 1,2,3,4,5-pentamethylferrocene⁴⁶ was synthesized from iron(II)bis(acetylacetonate)⁴⁷ according to literature procedures. Ferrocene and 1,2,3,4,5-pentamethylferrocne were oxidized with AgPF₆ according to literature procedures.^{48 (link) 1}H NMR spectra were recorded at ambient temperature on either an A400 or A500 DD2 Agilent spectrometer operating at 400 MHz or 500 MHz, respectively. Spectra were referenced to the residual solvent signal (5.32 ppm) for CHDCl₂. UV-vis spectra were recorded on an Agilent Cary 60 spectrophotometer. IR spectra were recorded inside a Nitrogen filled glovebox with a Bruker Alpha FT-IR spectrometer using a CsF liquid cell with a 1 mm pathlength. Kinetic measurements were recorded on an OLIS-RSM 1000 single mixing stopped flow spectrophotometer in anaerobic methylene chloride solvent. Full details of these and other measurements are given in the Supplementary Information.