The reactions of tridentate cationic palladium(II) complexes with olefins and nucleophiles

The reaction of the chelating bisphosphine 1,3-bis(diphenylphosphino)xylene (dppxH) 1 with PdCl₂(NCMe)₂ gives (dppx)PdCl 3. Analogously, 1,3-bis(bis(p-dimethylaniline)phosphino)xylene (dappxH) 2 yields (dappx)PdCl 4. Halide abstraction with AgBF₄ leads cleanly to the ionic complexes [(dppx)Pd-solv]⁺ (BF₄)^- 5 and [(dappx)Pd-solv]⁺ (BF₄)^- 6 (solv = solvent); in solution, there is no evidence for interaction between anion and cation. Norbornene adds to 5 and 6 to give the corresponding olefin complexes [(dppx)Pd(nor)]⁺ (BF₄)^- 7 [(dappx)Pd(nor)]⁺(BF₄)^- 8. The olefin is only weakly bound to the metal center and can be easily displaced by nucleophiles, as demonstrated by the reaction of 7 with HO^-, MeO^-, CH₂ = CH(CH₂)₄)O^- and NH₂Ph, to give the corresponding Pd(II)-Nuc complexes, (dppx)PdOH 10, (dppx)PdOMe 11, (dppx)PdO(CH₂)₄CHCH₂ 12 and [(dppx)-PdNH₂Ph]⁺(BF₄)^- 13. The crystal structure of [(dppx)PdNH₂Ph]⁺(BF₄)·1.5 CH₂Cl₂ 13 has been determined by an X-ray diffraction study at 113 K. The angle P(1)PdP(2) is 160.8(3)°, indicating substantial steric congestion because of the size of the aniline ligand. In the solid state, cation and anion are associated via hydrogen bonding in a NH ...· F bridge.