Synthesis, Characterization, and Electrochemical Properties of a Series of Sterically Varied Iron(II) Alkoxide Precursors and Their Resultant Nanoparticles

A new family of iron(II) aryloxide [Fe(OAr)(2)(py)(x)] precursors was synthesized from the alcoholysis of iron(II) mesityl [Fe(Mes)(2)] in pyridine (py) using a series of sterically varied 2-alkyl phenols (alkyl = methyl (H-oMP), isopropyl (H-oPP), tert-butyl (H-oBP)) and 2,6-dialkyl phenols (alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), phenyl (H-DPhP)). All of the products were found to be mononuclear and structurally characterized as [Fe(OAr)(2)(py)(x)] (x = 3 OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5); x = 2 OAr = DBP (6), DPhP (7)). The use of tris-tert-butoxysilanol (OSi(OBut)(3) = TOBS) led to isolation of [Fe(TOBS)(2)(py)(2)] (8). The new Fe(OAr)(2)(py)(x) (1-6) were found, under solvothermal conditions, to produce nanodots identified by PXRD as the gamma-maghemite phase. The model precursor 3 and the nanoparticles 6n were evaluated using electrochemical methods. Cyclic voltammetry for 3 revealed multiple irreversible oxidation peaks, which have been tentatively attributed to the loss of alkoxide ligand coupled with the deposition of a solid Fe-containing coating on the electrode. This coating was stable out to the voltage limits for the acetonitrile solvent.