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(O,O-acac)] (48 VEC) with [HPPh3][ClO4] gives the 46 VEC unsaturated [(C6F5)2Pt1(μ-PPh2)2Pt2(μ- PPh2)2Pt3(PPh3)](Pt2–Pt3) (1), a trinuclear compound endowed with a Pt-Pt bond. This compound displays amphiphilic behaviour and reacts easily with nucleophiles L yielding the saturated complexes [(C6F5)2PtII(μ-PPh2)2PtII(μ-PPh2)2PtII(PPh3)L] (L = PPh3 2, py 3). The reaction with the electrophile [Ag(OClO3)PPh3] affords the adduct 1·AgPPh3 that evolves, even at low temperature, to a mixture in which [(C6F5)2PtIII(μ- PPh2)2PtIII(μ-PPh2)2PtII(PPh3)2]2+(PtIII–PtIII) and 2 (plus silver metal) are present. The nucleophilic nature of 1 is also demonstrated through its reaction with cis- [Pt(C6F5)2(thf)2] which results in the formation of [Pt4(μ-PPh2)4(C6F5)4(PPh3)], 4. The structure and NMR features indicate that 1 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 (DFT) 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 employing a multitude of computational techniques (NBO analysis, the Laplacian of the electron density and the Localized Orbital Locator (LOL) profiles).