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

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)C l-3] [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 t o Au(I) with a linear geometry. Complexes 1-4 were characterised by microan alysis, FAB mass spectrometry, IR, NMR (P-31 and Pt-195) spectroscopies and conductivity measurements. Complexes 2-4 were also characterised by X-ray crystallography. [Pt(triphos)Cl]Cl, 2, is monoclinic, space group P2(1)/n, with square-planar geometry. The Pt-P-central bond distance (2.207 Angstrom ) is shorter than the other two Pt-P distances (2.312 and 2.315 Angstrom). [PdAu(triphos)Cl-3], 3, is also monoclinic (space group P2(1)/n), with squa re-planar Pd(II) and linear Au(I) (P-Au-Cl 177.73 degrees), and has a simil ar structure to complex 4, [PtAu(triphos)Cl-3] (monoclinic, space group I2/ a). The thiolate S of the tripeptide glutathione (GSH) and N-acetyl-L-cyste ine binds to [Pt(triphos)](2+) giving adducts with high aqueous solubility. In the presence of Au(I), 5'-GMP displaced glutathione from [Pt(triphos)(G S)](+) to form two adducts. Both GSH and N-acetyl-L-cysteine readily extrac ted Au(I) from complex 4, [PtAu(triphos)Cl-3], to give complex 2, [Pt(triph os)Cl]Cl, and the Au(I) thiolate. Since chloride and thiolates would be str ong competitors to DNA binding, proteins could be possible target sites for these complexes.