Role of Axial Ligation in Gating the Reactivity of Dimethylplatinum(III) Diimine Radical Cations

Electrochemical methods are coupled with chemical oxidant-based analytical strategies to evaluate the oxidative reactivity of the platinum­(II) diimine complex (bpy)­PtII(CH3)2 (bpy = 2,2′-bipyridine) in coordinating and noncoordinating media. Through this mechanistic analysis, we show that the one-electron oxidation of (bpy)­PtII(CH3)2 generates a highly reactive, 15-electron PtIII radical cation and identify three reaction pathways that can follow this oxidation: radical–substrate dimerization, radical–radical dimerization, and oxidative disproportionation. Axial ligation of the initially generated [(bpy)­PtIII(CH3)2]•+ species is a critical driver of this reactivity, gating the available mechanistic pathways and tuning the competition between radical–radical dimerization and oxidative disproportionation.