More recently, a detailed mechanistic study of a Nicatalyzed C-O bond formation between alcohols and aryl halides was carried out by Mirica and coworkers. In this work, a tridentate pyridinophane ligand was developed to stabilize Ni(I/III) and utilized to obtain evidence in the form of EPR and stoichiometric studies that supports oxidative addition at Ni(I), binding of the alcohol substrate to Ni(III), deprotonation by the base, and finally reductive elimination to form the aryl ether product. In the case where they use Ir(ppy)3 as a PC, oxidative quenching was proposed on the basis of a redox argument and the observation that product only formed with sufficiently reducing PCs. Although this work is a significant advance in terms of elucidating the reactivity of Ni(I) and Ni(III) intermediates, experimental evidence for the photoreduction of Ni(II) to Ni(I) remains elusive.