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)Pt-II(CH3)(2) (bpy = 2,2'-bipyridine) in coordinating and noncoordinating media. Through this mechanistic analysis, we show that the one-electron oxidation of (bpy)Pt-II(CH3)(2) generates a highly reactive, 15-electron Pt-II 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)Pt-II(CH3)(2)](center dot+) species is a critical driver of this reactivity, gating the available mechanistic pathways and tuning the competition between radical-radical dimerization and oxidative disproportionation.