Water and Protic Acids as Oxidants for Platinum(II):  Diorgano(hydrido)platinum(IV) and Diorgano(hydroxo)platinum(IV) Chemistry, Including Structural Studies of Poly(pyrazol-1-yl)borate Complexes Pt(OH)R<sub>2</sub>{(pz)<sub>3</sub>BH} (R = Methyl, <i>p</i>-Tolyl) and Pt(OH)Me<sub>2</sub>{(pz)<sub>4</sub>B}·H<sub>2</sub>O

The tris(pyrazol-1-yl)borate complexes K[PtR<sub>2</sub>{(pz)<sub>3</sub>BH}] (R = Me (<b>1</b>), <i>p</i>-tolyl (<b>2</b>)) may be isolated on addition of K[(pz)<sub>3</sub>BH] to solutions of [PtR<sub>2</sub>(SEt<sub>2</sub>)]<sub>2</sub>. Complexes <b>1</b>, <b>2</b>, and [PtMe<sub>2</sub>{(pz)<sub>4</sub>B}]<sup>-</sup> react with acetic acid to form PtHR<sub>2</sub>{(pz)<sub>3</sub>BH} (R = Me (<b>3</b>), <i>p</i>-tolyl (<b>5</b>)) and PtHMe<sub>2</sub>{(pz)<sub>4</sub>B} (<b>4</b>). The hydridoplatinum(IV) complexes decompose at ∼140 (<b>3</b>) and ∼85 (<b>4</b>) °C in toluene-<i>d</i><sub>8</sub> and ∼90 °C (<b>5</b>) in nitrobenzene-<i>d</i><sub>5</sub> to form methane (<b>3</b>, <b>4</b>) and toluene (<b>5</b>), where isolation of <b>5</b> has provided the first opportunity to study the decomposition of aryl(hydrido)platinum(IV) complexes. The hydridoplatinum(IV) complexes are deprotonated on addition of aqueous sodium hydroxide in acetone-<i>d</i><sub>6</sub> to form <b>1</b>, <b>2</b>, and [PtMe<sub>2</sub>{(pz)<sub>4</sub>B}]<sup>-</sup>. The hydroxoplatinum(IV) complexes Pt(OH)R<sub>2</sub>{(pz)<sub>3</sub>BH} (R = Me (<b>6</b>), <i>p</i>-tolyl (<b>8</b>)) or Pt(OH)Me<sub>2</sub>{(pz)<sub>4</sub>B}·H<sub>2</sub>O (<b>7</b>) may be readily isolated in 45−82% yield upon oxidation of the platinum(II) anions <b>1</b>, <b>2</b>, or [PtMe<sub>2</sub>{(pz)<sub>4</sub>B}]<sup>-</sup> by water. The hydridoplatinum(IV) complexes <b>3</b>−<b>5</b> also react slowly with water in acetone-<i>d</i><sub>6</sub> to form hydrogen and complexes <b>6</b>−<b>8</b>. The anions [PtR<sub>2</sub>{(pz)<sub>3</sub>BH}]<sup>-</sup> undergo oxidative-addition reactions with iodomethane to form PtMeR<sub>2</sub>{(pz)<sub>3</sub>BH} (R = Me, <i>p</i>-tolyl). The octahedral hydroxoplatinum(IV) complexes <b>6</b>−<b>8</b> are the first examples of platinum(IV) complexes formed on oxidation by water to be characterized by X-ray crystallography. The complexes display Pt−O distances of 1.974(8)−1.996(6) Å, and the Pt−N bond distances reflect the relative trans influences of the hydroxo and methyl groups. The aqua group in Pt(OH)Me<sub>2</sub>{(pz)<sub>4</sub>B}·H<sub>2</sub>O (<b>7</b>) is hydrogen-bonded to the hydroxoplatinum(IV) group to form a centrosymmetric dimer, such that it is not possible to ascertain whether the coordination environment of platinum is [Pt(OH)···H<sub>2</sub>O]<sub>2</sub> or [Pt(OH<sub>2</sub>)<sup>+</sup>···OH<sup>-</sup>]<sub>2</sub>, although the former is believed to be more likely.