Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: synthesis, characterization and reactivity. Crystal and molecular structures of [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)] and [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{μ-Ph2P(CH2)4PPh2}][CF3SO3]2

Abstract

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}(PPh₃)][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-Ph₂PC₅H₄FeC₅H₄PPh₂)], 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)₄PPh₂}][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}{Ph₂P(CH₂)₂PPh₂-P,P}][ClO₄], 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}{(Ph₂PCH₂CH₂)₂PPh-P,P,P}][ClO₄], 9, in which the triphosphine is bonded to the palladium atom through the three phosphorus atoms.