Description:
<jats:title>Abstract</jats:title><jats:p>Electrospray ionization (ESI) of tetrameric platinum(II) acetate, [Pt<jats:sub>4</jats:sub>(CH<jats:sub>3</jats:sub>COO)<jats:sub>8</jats:sub>], in methanol generates the formal platinum(III) dimeric cation [Pt<jats:sub>2</jats:sub>(CH<jats:sub>3</jats:sub>COO)<jats:sub>3</jats:sub>(CH<jats:sub>2</jats:sub>COO)(MeOH)<jats:sub>2</jats:sub>]<jats:sup>+</jats:sup>, which, upon harsher ionization conditions, sequentially loses the two methanol ligands, CO<jats:sub>2</jats:sub>, and CH<jats:sub>2</jats:sub>COO to form the platinum(II) dimer [Pt<jats:sub>2</jats:sub>(CH<jats:sub>3</jats:sub>COO)<jats:sub>2</jats:sub>(CH<jats:sub>3</jats:sub>)]<jats:sup>+</jats:sup>. Next, intramolecular sequential double hydrogen‐atom transfer from the methyl group concomitant with the elimination of two acetic acid molecules produces Pt<jats:sub>2</jats:sub>CH<jats:sup>+</jats:sup> from which, upon even harsher conditions, PtCH<jats:sup>+</jats:sup> is eventually generated. This degradation sequence is supported by collision‐induced dissociation (CID) experiments, extensive isotope‐labeling studies, and DFT calculations. Both PtCH<jats:sup>+</jats:sup> and Pt<jats:sub>2</jats:sub>CH<jats:sup>+</jats:sup> react under thermal conditions with the hydrocarbons C<jats:sub>2</jats:sub>H<jats:sub><jats:italic>n</jats:italic></jats:sub> (<jats:italic>n</jats:italic>=2, 4, 6) and C<jats:sub>3</jats:sub>H<jats:sub><jats:italic>n</jats:italic></jats:sub> (<jats:italic>n</jats:italic>=6, 8). While, in ion–molecule reactions of PtCH<jats:sup>+</jats:sup> with C<jats:sub>2</jats:sub> hydrocarbons, the relative rates decrease with increasing <jats:italic>n</jats:italic>, the opposite trend holds true for Pt<jats:sub>2</jats:sub>CH<jats:sup>+</jats:sup>. The Pt<jats:sub>2</jats:sub>CH<jats:sup>+</jats:sup> cluster only sluggishly reacts with C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub>, but with C<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub> and C<jats:sub>2</jats:sub>H<jats:sub>6</jats:sub> dihydrogen loss dominates. The reactions with the latter two substrates were preceded by a complete exchange of all of the hydrogen atoms present in the adduct complex. The PtCH<jats:sup>+</jats:sup> ion is much less selective. In the reactions with C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub> and C<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>, elimination of H<jats:sub>2</jats:sub> occurs; however, CH<jats:sub>4</jats:sub> formation prevails in the decomposition of the adduct complex that is formed with C<jats:sub>2</jats:sub>H<jats:sub>6</jats:sub>. In the reaction with C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub>, in addition to H<jats:sub>2</jats:sub> loss, C<jats:sub>3</jats:sub>H<jats:sub>3</jats:sub><jats:sup>+</jats:sup> is produced, and this process formally corresponds to the transfer of the cationic methylidyne unit CH<jats:sup>+</jats:sup> to C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub>, accompanied by the release of neutral Pt. In the ion–molecule reactions with the C<jats:sub>3</jats:sub> hydrocarbons C<jats:sub>3</jats:sub>H<jats:sub>6</jats:sub> and C<jats:sub>3</jats:sub>H<jats:sub>8</jats:sub>, dihydrogen loss occurs with high selectivity for Pt<jats:sub>2</jats:sub>CH<jats:sup>+</jats:sup>, but in the reactions of these substrates with PtCH<jats:sup>+</jats:sup> several reaction routes compete. Finally, in the ion–molecule reactions with ammonia, both platinum complexes give rise to proton transfer to produce NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup>; however, only the encounter complex generated with PtCH<jats:sup>+</jats:sup> undergoes efficient dehydrogenation of the substrate, and the rather minor formation of CNH<jats:sub>4</jats:sub><jats:sup>+</jats:sup> indicates that CN bond coupling is inefficient.</jats:p>