Synthesis and Reactivity of the Unsaturated Trinuclear Phosphanido Complex [(C₆F₅)₂Pt(μ-PPh₂)₂Pt(μ-PPh₂)₂Pt(PPh₃)]

The reaction of [NBu₄]­[(C₆F₅)₂Pt­(μ-PPh₂)₂Pt­(μ-PPh₂)₂Pt­(<i>O</i>,<i>O</i>-acac)] (48 VEC) with [HPPh₃]­[ClO₄] gives the 46 VEC unsaturated [(C₆F₅)₂Pt¹(μ-PPh₂)₂Pt²(μ-PPh₂)₂Pt³(PPh₃)]­(Pt²–Pt³) (<b>1</b>), a trinuclear compound endowed with a Pt–Pt bond. This compound displays amphiphilic behavior and reacts easily with nucleophiles L, yielding the saturated complexes [(C₆F₅)₂Pt^II(μ-PPh₂)₂Pt^II(μ-PPh₂)₂Pt^II(PPh₃)­L] [L = PPh₃ (<b>2</b>), py (<b>3</b>)]. The reaction with the electrophile [Ag­(OClO₃)­PPh₃] affords the adduct <b>1</b>·AgPPh₃, which evolves, even at low temperature, to a mixture in which [(C₆F₅)₂Pt^III(μ-PPh₂)₂Pt^III(μ-PPh₂)₂Pt^II(PPh₃)₂]²⁺(Pt^III–Pt^III) and <b>2</b> (plus silver metal) are present. The nucleophilic nature of <b>1</b> is also demonstrated through its reaction with <i>cis</i>-[Pt­(C₆F₅)₂(THF)₂], which results in the formation of [Pt₄(μ-PPh₂)₄(C₆F₅)₄(PPh₃)] (<b>4</b>). The structure and NMR features indicate that <b>1</b> can be better considered as a Pt^II–Pt^III–Pt^I complex instead of a Pt^II–Pt^II–Pt^II derivative. Theoretical calculations (density functional theory) on similar model compounds are in agreement with the assigned oxidation states of the metal centers. The strong intermetallic interactions resulting in a Pt²–Pt³ metal–metal bond and the respective bonding mechanism were verified by employing a multitude of computational techniques (natural bond order analysis, the Laplacian of the electron density, and localized orbital locator profiles)