| Summary: | Pt<sup>IV</sup> coordination complexes are of interest as prodrugs of Pt<sup>II</sup> anticancer agents, as they can avoid deactivation pathways owing to their inert nature. Here, we report the oxidation of the antitumor agent [Pt<sup>II</sup>(<i>p</i>-BrC<sub>6</sub>F<sub>4</sub>)NCH<sub>2</sub>CH<sub>2</sub>NEt<sub>2</sub>}Cl(py)], <b>1</b> (py = pyridine) to dihydroxidoplatinum(IV) solvate complexes [Pt<sup>IV</sup>{(<i>p</i>-BrC<sub>6</sub>F<sub>4</sub>)NCH<sub>2</sub>CH<sub>2</sub>NEt<sub>2</sub>}Cl(OH)<sub>2</sub>(py)].H<sub>2</sub>O, <b>2·H<sub>2</sub>O</b> with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) at room temperature. To optimize the yield, <b>1</b> was oxidized in the presence of added lithium chloride with H<sub>2</sub>O<sub>2</sub> in a 1:2 ratio of Pt: H<sub>2</sub>O<sub>2,</sub> in CH<sub>2</sub>Cl<sub>2</sub> producing complex <b>2·H<sub>2</sub>O</b> in higher yields in both gold and red forms. Despite the color difference, red and yellow <b>2·H<sub>2</sub>O</b> have the same structure as determined by single-crystal and X-ray powder diffraction, namely, an octahedral ligand array with a chelating organoamide, pyridine and chloride ligands in the equatorial plane, and axial hydroxido ligands. When tetrabutylammonium chloride was used as a chloride source, in CH<sub>2</sub>Cl<sub>2</sub>, another solvate, [Pt<sup>IV</sup>{(<i>p</i>-BrC<sub>6</sub>F<sub>4</sub>)NCH<sub>2</sub>CH<sub>2</sub>NEt<sub>2</sub>}Cl(OH)<sub>2</sub>(py)].0.5CH<sub>2</sub>Cl<sub>2,</sub><b>3·0.5CH<sub>2</sub>Cl<sub>2</sub></b>, was obtained. These Pt<sup>IV</sup> compounds show reductive dehydration into Pt<sup>II</sup> [Pt{(<i>p</i>-BrC<sub>6</sub>F<sub>4</sub>)NCH=CHNEt<sub>2</sub>}Cl(py)], <b>1H</b> over time in the solid state, as determined by X-ray powder diffraction, and in solution, as determined by <sup>1</sup>H and <sup>19</sup>F NMR spectroscopy and mass spectrometry. <b>1H</b> contains an oxidized coordinating ligand and was previously obtained by oxidation of <b>1</b> under more vigorous conditions. Experimental data suggest that oxidation of the ligand is favored in the presence of excess H<sub>2</sub>O<sub>2</sub> and elevated temperatures. In contrast, a smaller amount (1Pt:2H<sub>2</sub>O<sub>2</sub>) of H<sub>2</sub>O<sub>2</sub> at room temperature favors the oxidation of the metal and yields platinum(IV) complexes.
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