Addition of Nucleophiles to Phosphanido Derivatives of Pt(III): Formation of P-C, P-N and P-O Bonds

The reactivity of the dinuclear platinum(III) derivative [(RF)2PtIII(μ-PPh2)2PtIII(RF)2](Pt−Pt) (RF = C6F5) (1) toward OH−, N3 −, and NCO− was studied. The coordination of these nucleophiles to a metal center evolves with reductive coupling or reductive elimination between a bridging diphenylphosphanido group and OH−, N3 −, and NCO− or C6F5 groups and formation of P−O, P−N, or P−C bonds. The addition of OH− to 1 evolves with a reductive coupling with the incoming ligand, formation of a P−O bond, and the synthesis of [NBu4]2[(RF)2PtII(μ-OPPh2)(μ-PPh2)- PtII(RF)2] (3). The addition of N3 − takes place through two ways: (a) formation of the P−N bond and reductive elimination of PPh2N3 yielding [NBu4]2[(RF)2PtII(μ-N3)(μ-PPh2)PtII(RF)2] (4a) and (b) formation of the P−C bond and reductive coupling with one of the C6F5 groups yielding [NBu4][(RF)2PtII(μ-N3)(μ- PPh2)PtII(RF)(PPh2RF)] (4b). Analogous behavior was shown in the addition of NCO− to 1 which afforded [NBu4]2[(RF)2PtII(μ-NCO)(μ-PPh2)PtII(RF)2] (5a) and [NBu4][(RF)2PtII(μ-NCO)(μ-PPh2)PtII(RF)(PPh2RF)] (5b). In the reaction of the trinuclear complex [(RF)2PtIII(μ-PPh2)2PtIII(μ-PPh2)2PtII(RF)2](PtIII−PtIII) (2) with OH− or N3 −, the coordination of the nucleophile takes place selectively at the central platinum(III) center, and the PPh2/OH− or PPh2/N3 − reductive coupling yields the trinuclear [NBu4]2[(RF)2PtII(μ-Ph2PO)(μ-PPh2)PtII(μ-PPh2)2PtII(RF)2] (6) and [NBu4]- [(RF)2Pt1(μ3-Ph2PNPPh2)(μ-PPh2)Pt2(μ-PPh2)Pt3(RF)2](Pt2−Pt3) (7). Complex 7 is fluxional in solution, and an equilibrium consisting of Pt−Pt bond migration was ascertained by 31P EXSY experiments.