Trimethyl-palladium(IV) and -platinum(IV) complexes containing phosphine donor ligands, including studies of 1,5,9-triethyl-1,5,9-triphosphacyclodecane and X-ray structural studies of palladium(II) and palladium(IV) complexes

Abstract

Dimethyl(2,2′-bipyridine)palladium(II) reacted with methyl triflate (CF₃SO₃Me) at −60 °C to form a palladium(IV) complex which reacted with a range of monodentate phosphines [PPh₃, PMePh₂, PMe₂Ph, PCy₃, P(OMe)₃], 1,2-bis(diethylphosphino)ethane (depe), or syn,syn-1,5,9-triethyl-1,5,9-triphosphacyclodecane (syn,syn-Et₃[12]aneP₃) to form complexes containing octahedral palladium(IV) centres fac-[PdMe₃(2,2′-bipy)(L)]⁺1–5, 11–13. The ligand depe bridges between palladium(IV) centres in a binuclear complex (11), the triphosphine forms both mononuclear (13) and binuclear species (12), and representative complexes of other bidentate nitrogen donor ligands have also been prepared, [PdMe₃(N–N)(PMe₂Ph)][O₃SCF₃] [N–N = 1,10-phenanthroline (phen) 6 or N,N,N′,N′-tetramethylethylenediamine (tmen) 7]. The first structural analysis of an organopalladium(IV) phosphine complex is reported, and octahedral 6 and platinum(IV) complexes [PtMe₃(2,2′-bipy)(L)][O₃SCF₃] [L = PPh₃8, PMePh₂9 or PMe₂Ph 10] have been isolated. All of the palladium(IV) complexes reductively eliminate ethane on decomposition to form palladium(II) species, where the monodentate phosphines form [PdMe(N–N)(L)]⁺1a–7a; a structural analysis of square-planar [PdMe(2,2′-bipy)(PMe₂Ph)][O₃SCF₃] 3a is reported. The stability of palladium(IV) complexes decreases in the order PMe₂Ph > PMePh₂ > PPh₃, and for complexes of PMe₂Ph there is a stability order phen > 2,2′-bipy > tmen for [PdMe₃(bidentate ligand)(PMe₂Ph)]⁺.