Electrochemical Characterization of (R-,R′-bpy)Os(Cl)2(=O)2 Complexes Presenter

This project involved the 1-step synthesis and characterization of osmium complexes following the chemical formula, (R-,R′-bpy)Os(Cl)2(=O)2, where R represents a variety of carbon-based groups such as tert-butyl (–C(CH3)3), methoxy (–OCH3), and trifluoromethyl (–C(CF3)3). These osmium complexes are a marked improvement over osmium tetroxide, which is volatile and extremely hazardous. Furthermore, previous studies of these complexes were limited to stoichiometric use with harsh oxidants, whereas we propose catalysis using only water and green energy inputs (e.g. electricity). Herein, we evaluated the ability of these complexes to oxidize thioethers (70-80% yield), via the input of a mild, applied current or potential. Specifically, these complexes were observed to undergo an initial activation step: 1) reduction followed by 2) geometric reorganization. Subsequent reoxidation of this species formed the active complex for catalysis. To inform these claims, we used a combination of electrochemistry (cyclic voltammetry, chronoamperometry), spectroelectrochemistry (ultraviolet-visible), and spectroscopy (electron-paramagnetic resonance, nuclear magnetic resonance) techniques. Additionally, further understanding of the complex was achieved through computational modeling, which was used to explain the initial activation step involving chloride dissociation and/or halide exchange.