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.