Gold(I)-induced chelate ring-opening of palladium(II) and platinum(II) triphos complexes

Abstract

The complexes [M(triphos)Cl]Cl [triphos = PhP(CH₂CH₂PPh₂)₂; M = Pd (1), M = Pt (2)] undergo ring-opening reactions with Au(I) to give [MAu(triphos)Cl₃] [M = Pd (3), M = Pt (4) ]. In these mixed metal complexes, triphos acts as a bidentate ligand for M and the third phosphorus atom is coordinated to Au(I) with a linear geometry. Complexes 1–4 were characterised by microanalysis, FAB mass spectrometry, IR, NMR (³¹P and ¹⁹⁵Pt) spectroscopies and conductivity measurements. Complexes 2–4 were also characterised by X-ray crystallography. [Pt(triphos)Cl]Cl, 2, is monoclinic, space group P2₁/n, with square-planar geometry. The Pt–P_central bond distance (2.207 Å) is shorter than the other two Pt–P distances (2.312 and 2.315 Å). [PdAu(triphos)Cl₃], 3, is also monoclinic (space group P2₁/n), with square-planar Pd(II) and linear Au(I) (P–Au–Cl 177.73°), and has a similar structure to complex 4, [PtAu(triphos)Cl₃] (monoclinic, space group I2/a). The thiolate S of the tripeptide glutathione (GSH) and N-acetyl-L-cysteine binds to [Pt(triphos)]²⁺ giving adducts with high aqueous solubility. In the presence of Au(I), 5′-GMP displaced glutathione from [Pt(triphos)(GS)]⁺ to form two adducts. Both GSH and N-acetyl-L-cysteine readily extracted Au(I) from complex 4, [PtAu(triphos)Cl₃], to give complex 2, [Pt(triphos)Cl]Cl, and the Au(I) thiolate. Since chloride and thiolates would be strong competitors to DNA binding, proteins could be possible target sites for these complexes.