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)Pt(μ-PhPO)(μ-PPh)Pt(μ-PPh)Pt(solv)(solv′)] [(1-(solv)(solv′)] (solv, solv′ = acetone, HO, CHCN) has been prepared by reaction of [(R)Pt(μ-PPh)Pt(μ-PPh)Pt(NCCH)] with AgClO in CHCN/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 [(CF)Pt(μ-PPh)(μ-PPhO)Pt(μ-PPh)Pt(dppm)] (2) or [NBu][(CF)Pt(μ-PPh)(μ-PPhO)Pt(μ-PPh)Pt(μ-Cl)Pt(μ-PPh)Pt(μ-PPh)(μ-PPhO)Pt(CF)] (as a mixture of the two possible isomers 4a and 4b). Complex 2 reacts with AgClO to form the tetranuclear derivative [(CF)Pt(μ-PPh)(μ-PPhO)Pt(μ-PPh)Pt(dppm)Ag(OClO)] (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 [NBu][(CF)Pt(μ-PPh)(μ-PPhO)Pt(μ-PPh)Pt(acac)] (5) which, upon reaction with HCl, yields back the mixture of 4a-4b. The reaction of 4a-4b with PPh produces [NBu][(CF)Pt(μ-PPh)(μ-PPhO)Pt(μ-PPh)Pt(Cl)(PPh)] (6) as a mixture of isomers with the chloro ligand located syn (6a) or anti (6b) to the PPhO group. Either the reaction of 6 with AgClO or the treatment of 5 with HPPhClO results in the formation of the species [(CF)Pt(μ-PPh)Pt(μ-PPhOPPh)Pt(PPh)] (7) (44 VEC), which can be explained as the consequence of a PPhO/PPh 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.