Intramolecular Csp<sup>3</sup>‑H Activation\nat a Platinum(IV) Center Resulting from O<sub>2</sub> Activation:\nThe Role of a Proton-Responsive Ligand and Trans Influence

Aerobic\noxidation of a dimethylplatinum(II) complex featuring\n1,1-di(2-pyridyl)ethanol\nas a supporting ligand leads to the formation of two unexpected Pt<sup>IV</sup> complexes (in ∼1:1 ratio), neither of which results\nfrom direct oxidation typical for Pt<sup>II</sup> centers supported\nby popular κ<sup>2</sup>-(<i>N</i>,<i>N</i>) ligands. While one product features an isomerized Pt<sup>IV</sup> center stabilized by the κ<sup>3</sup>-(<i>N</i>,<i>N</i>,<i>O</i>) ligand coordination mode,\nsurprisingly, the other product results from intramolecular activation\nof the ligand methyl fragment. Mechanistic studies, reactivity of\nmodel complexes, and DFT calculations reveal that the critical proton-responsive\nnature of the ligand allows formation of intermediates that result\nin a concerted metalation deprotonation (CMD)-like C–H activation\nat Pt<sup>IV</sup>. To the best of our knowledge, this is the first\nmechanistic delineation of Csp<sup>3</sup>-H activation at Pt<sup>IV</sup>, despite being known for other high-valent platinum group\nmetal centers.