Intramolecular Csp³-H Activation at a Platinum(IV) Center Resulting from O₂ Activation: The Role of a Proton-Responsive Ligand and Trans Influence

Aerobic oxidation of a dimethylplatinum(II) complex featuring 1,1-di(2-pyridyl)ethanol as a supporting ligand leads to the formation of two unexpected Pt^IV complexes (in ∼1:1 ratio), neither of which results from direct oxidation typical for Pt^II centers supported by popular κ²-(<i>N</i>,<i>N</i>) ligands. While one product features an isomerized Pt^IV center stabilized by the κ³-(<i>N</i>,<i>N</i>,<i>O</i>) ligand coordination mode, surprisingly, the other product results from intramolecular activation of the ligand methyl fragment. Mechanistic studies, reactivity of model complexes, and DFT calculations reveal that the critical proton-responsive nature of the ligand allows formation of intermediates that result in a concerted metalation deprotonation (CMD)-like C-H activation at Pt^IV. To the best of our knowledge, this is the first mechanistic delineation of Csp³-H activation at Pt^IV, despite being known for other high-valent platinum group metal centers.