Iron Complexes as Catalysts for Electrochemical Atom Transfer Radical Addition

Iron complexes of the tetradentate ligand tris(2-pyridylmethyl)amine (TPMA) have been extensively studied as catalysts in oxidative transformations of organic substrates. Herein we have applied them as catalysts in electrochemical atom transfer radical addition (ATRA) of bromoacetonitrile to styrene. A family of Fe-TPMA complexes comprising mononuclear [FeII(TPMA)(NCMe)2]2+ and [FeIII(TPMA)Cl2]+ as well as μ-oxido di-Fe complexes [(L(TPMA)FeIII)2O]n+ (L = H2O (n = 4); Cl–, Br– (n = 2)) were studied, which were structurally characterized and electrochemically analyzed in acetonitrile. Yields of ATRA product were dependent on the coligands present and in contrast to their highly reactive Cu-TPMA complexes, radical activation appears to be slower but advantageously this leads to fewer side products.