The majority of mechanisms proposed for Fe catalysed oxidative cross-couplings are based upon an Fe(III)/Fe(IV) cycle, which broadly parallel the accepted mechanisms for the operation of heme-containing enzymes . Crosscoupling selectivity in non-heme systems are usually determined by differences in oxidation potentials that control which cross-coupling partner is oxidized preferentially, in conjunction with other parameters that influence nucleophilicity and acidity . To probe the determinants of reactivity and selectivity in our system, we measured the oxidation potentials of 2-tert-butyl indole (0.71 V vs Ag/AgCl) and 2-isopropylphenyl 3-hydroxy-2-naphthoate (1.42 V vs Ag/AgCl) in HFIP. These measurements clearly show that under these conditions the indole is significantly easier to oxidize than the naphthol component. To determine whether our oxidation state measurements were reflected by the presence of radical species in solution, we employed EPR spectroscopy (Figure ). We were able to observe a species (g = 2.0051) in low spin concentration that we identified as the indole radical (by virtue of its characteristic 14 N hyperfine signature) by stirring the indole in HFIP/DCE without precautions to exclude oxygen.