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

摘要

The complexes [M(triphos)Cl]Cl [triphos = PhP(CH_2CH_2PPh_2)_2; M = Pd (1), M = Pt (2)] undergo ring-opening reactions with Au(I) to give [MAu(triphos)Cl_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 to Au(I) with a linear geometry. Complexes 1-4 were characterised by microanalysis, FAB mass spectrometry, IR, NMR ~(31)P and ~(195)Pt) 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, with square-planar geometry. The Pt-P_(central) bond distance (2.207 A) is shorter than the other two Pt-P distances (2, 312 and 2.315 A). [PdAu(triphos)Cl_3], 3, is also monoclinic (space group P2_1), with square-planar Pd(II) and linear Au(I) (P-Au-Cl 177.73 deg C), and has a similar 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-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)Cl_3], 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.