Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: Synthesis, characterization and reactivity

Article abstract of DOI:10.1039/b106511d

Treatment of the Schiff base 2-ClC₆H₄C(H)=NCH₂CH₂SMe, 1, with palladium(II) acetate in dry toluene gave the mononuclear cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe} (O₂CMe)], 2. Reaction of 2 with aqueous sodium chloride gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe} (Cl)], 3, after a metathesis reaction. The X-ray crystal structure of 3 was determined and shows that the palladium atom is bonded to four different donor atoms: C, N, S and Cl. Treatment of 3 with triphenylphosphine in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}(Cl) (PPh₃)] with cleavage of the Pd-S bond. However, treatment of 3 with silver triflate and triphenylphosphine gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}(PPh ₃)][CF₃SO₃], 10, in which the Pd-S bond is retained. Reaction of 3 with the diphosphines dppm, dppb or dppf in a 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe] (Cl)}₂{μ-Ph₂P(CH₂)nPPh₂}], (n = 1, 5; n = 4, 6), and [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe] (Cl)}₂(μ-Ph₂PC₅H₄FeC ₅H₄PPh₂)], 7. Treatment of 3 with dppb in a 2:1 molar ratio and AgCF₃SO₃ gave the dinuclear cyclometallated complex [{Pd[2-ClC₆H₃C(H)=NCH₂CH₂SMe]} ₂{μ-Ph₂P(CH₂)₄PPh ₂}][CF₃SO₃]₂ , 11, which was characterized by X-ray crystal structure analysis. Reaction of 3 with dppe in a 1:1 molar ratio and sodium perchlorate gave the mononuclear complex [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}{Ph ₂P(CH₂)₂PPh₂-P,P}][ClO ₄], 8. Treatment of 3 with bis(2-diphenylphosphinoethyl)phenylphosphine in a 1:1 molar ratio, followed by treatment with sodium perchlorate gave [Pd{2-ClC₆H₃C(H)=NCH₂CH₂SMe}{(Ph ₂PCH₂CH₂)₂PPh-P,P,P}][ClO ₄], 9, in which the triphosphine is bonded to the palladium atom through the three phosphorus atoms.