Homonuclear Pd-II and Pt-II and heteronuclear (PdAuI)-Au-II and (PtAuI)-Au-II complexes of a tripod triphosphine ligand: Synthesis, characterization and reactions with molecules of biological relevance

Complexes of the type Pd( tripod)X-2 [tripod = MeC(CH2PPh2)(3); X = Cl (1), Br (2), I (3)] and Pt( tripod)X-2 [X = Cl (4), Br (5), I (6)] have been sy nthesized. In these complexes tripod acts as a bidentate chelating ligand. The uncoordinated phosphorus atom can bind to Au I to form the bimetallic c omplexes PdAu( tripod)X-3 [X = Cl (7), Br (8), I (9)] and PtAu(tripod)X-3 [ X = Cl (10), Br (11), I (12)]. Complexes (1) ( 12) have been characterized by microanalysis, f.a.b. mass spectrometry, i.r. spectroscopy, P-31 and Pt- 195 n.m.r. spectroscopies, and conductivity measurements. The structures of complexes (1), (4) and (11), as well as that of the unusual complex Cl2Pt( tripod) AuBr0.5Cl0.5 (13), isolated from reaction of Pt(tripod)Br-2 (5), an d [Au(thiodiglycol)Cl], have been determined. All complexes show square-pla nar geometry for Pd-II or Pt-II and linear geometry for Au-I. The X-ray cry stal structure of (1) showed partial oxidation of the dangling phosphorus o f the ligand in 50% of the molecule distributed randomly over the lattice. Reactions of complex (4), Pt(tripod)Cl-2, with the tripeptide glutathione ( GSH) showed the formation of [Pt-2(tripod)(2)(GS-mu S)(2)](2+) (15a). No re action with N-acetyl-L-methionine (AcMet) or guanosine 5'-monophosphate (5' -GMP) was observed. Reactions of [Pt(tripod-O)(ONO2)(2)] (14) with GSH resu lted in the formation of [Pt-2(tripod-O)(2)(GS-mu -S)(2)](2+) (15b). Displa cement of the S-containing molecules by 5'-GMP in the presence of Au-I, via Pt S bond cleavage, was observed for complex (15b). PtAu(tripod)Cl-3 (10) reacted with GSH, with initial attack on the Au-I centre.