We explored the oxidative chemistry of complex 1 in anticipation that higher valent states of cobalt may be stabilized by the Ph L 3-ligand. Interestingly, 1 reacts cleanly with dry O2 in C6D6 over 24 hours to give a new paramagnetic species (compound 2). The 1 H-NMR spectrum of 2 (Fig S25 ) exhibits six overlapping, paramagnetically-shifted resonances, consistent with a three-fold symmetric compound. Solution-phase magnetic measurements indicate that this species exhibits an S = 2 (4.94 µB) spin state at room temperature. The X-ray crystal structure of 2 reveals a mononuclear [ Ph L]Co compound featuring a formally-trivalent cobalt center bound to three terminal PN moieties (Fig ). Apparently, the addition of O2 to 1 results in its chemical oxidation to afford 2 and an insoluble, uncharacterized CoxOy byproduct. The conversion of 1 to 2 is also efficiently mediated by hexachloroethane (65% yield), and compound 2 is most conveniently prepared in one pot via treatment of H3 Ph L with 1 equivalent of Co[N(SiMe3)2]2(THF) followed by oxidation with 1 equivalent of C2Cl6 (68% yield).