PALLADIUM(II) AND PLATINUM(II) COMPLEXES WITH N-SUBSTITUTED METHIONINES

As an approach to systems containing methionine residues, 3-acetyl-4-h ydroxy-6-methyl-2H-pyran-2-one (HDh, dehydroacetic acid) was treated w ith L-methionine (MetH) or L-methionine methylester (MetM). By condens ation at the acyl group and transfer of the phenolic hydrogen on the n itrogen atom, the related ligands DhMetH and DhMetM, were isolated, an d form complexes of formula [MX2(L)2](M = Pd or Pt, L = DhMetM, X = Cl , Br or I; L = DhMetH, X = Cl or Br) and [MI2(DhMetH)] with palladium and platinum dihalides. The reaction of the DhMetK carboxylate with MC l2 in various media is discussed. Ligands and complexes were character ized by i.r. and n.m.r. (H-1 and C-13) spectroscopy and, in some cases , by thermogravimetric measurements. The ligands behave as monodentate sulphur donors, the 1:2 complexes showing a trans geometry except for [PtCl2(DhMetH)2], which is probably a mixture of cis and trans isomer s.