Polynuclear platinum phosphanido/phosphinito complexes: formation of P–O and P–O–P bonds through reductive coupling processes

Abstract

A mixture of the asymmetric complexes of formula [(R_F)₂Pt(μ-Ph₂PO)(μ-PPh₂)Pt(μ-PPh₂)₂Pt(solv)(solv′)] [(1-(solv)(solv′)] (solv, solv′ = acetone, H₂O, CH₃CN) has been prepared by reaction of [(R_F)₂Pt^II(μ-PPh₂)₂Pt^II(μ-PPh₂)₂Pt^II(NCCH₃)₂] with AgClO₄ in CH₃CN/acetone. The lability of the Pt–solvent bonds allows the displacement of the coordinated solvent molecules by dppm or Cl⁻ and the isolation of the tri- or hexanuclear phosphanido/phosphinito Pt(II) complexes [(C₆F₅)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(μ-PPh₂)₂Pt(dppm)] (2) or [NBu₄]₂[(C₆F₅)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(μ-PPh₂)₂Pt(μ-Cl)₂Pt(μ-PPh₂)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(C₆F₅)₂] (as a mixture of the two possible isomers 4a and 4b). Complex 2 reacts with AgClO₄ to form the tetranuclear derivative [(C₆F₅)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(μ-PPh₂)₂Pt(dppm)Ag(OClO₃)] (3), which displays two Pt–Ag donor–acceptor bonds. The mixture of the hexanuclear isomers 4a–4b reacts with Tl(acac) producing the acetylacetonato complex [NBu₄][(C₆F₅)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(μ-PPh₂)₂Pt(acac)] (5) which, upon reaction with HCl, yields back the mixture of 4a–4b. The reaction of 4a–4b with PPh₃ produces [NBu₄][(C₆F₅)₂Pt(μ-PPh₂)(μ-PPh₂O)Pt(μ-PPh₂)₂Pt(Cl)(PPh₃)] (6) as a mixture of isomers with the chloro ligand located syn (6a) or anti (6b) to the PPh₂O⁻ group. Either the reaction of 6 with AgClO₄ or the treatment of 5 with HPPh₃ClO₄ results in the formation of the species [(C₆F₅)₂Pt^II(μ-PPh₂)₂Pt^I(μ-PPh₂OPPh₂)Pt^I(PPh₃)] (7) (44 VEC), which can be explained as the consequence of a PPh₂O/PPh₂ reductive coupling and a rearrangement of ligands in the molecule generating a Pt(II),Pt(I),Pt(I) compound. All complexes were characterised in the solid state by XRD (only one of the isomers, in the cases of 4 and 6) and in solution by NMR spectroscopy.