Three new platinum(II)-dipeptide complexes

Three new platinum(II) complexes with the dipeptide ligands L-methionylglycine, L-prolylglycine and glycyl-L-histidine have been prepared and characterized structurally. In dichloro-L-methionylglycineplatinum(II) monohydrate (I), coordination of L-methionylglycine to the Pt atom via the N(amino) and S(thioether) atoms leads to the formation of a six-membered chelate ring. Neither the N(peptide) nor the O(peptide) atom interacts with the metal. In w-dimethylsulfoxide-L-prolylglycina dihydrate (II), L-prolylglycine coordinates the Pt atom via the N(imino) and N(peptide) atoms to form a five-membered chelate ring. The sulfur atom of the DMSO solvent is bonded trans to the N(imino) atom of the dipeptide. In chloro-glycyl-L-histidinatoplatinum (II) monohydrate (III), the glycyl-L-histidine is tridentate. The Pt atom is coordinated via the N(amino), N(peptide) and N-delta(imidazole) atoms so that there are adjacent five- and six-membered chelate rings. The carboxyl group of the dipeptide ligand in all three complexes I-III is protonated and does not participate in the coordination. The mechanisms of reactions that account for the formation of these complexes are discussed. (C)1999 Elsevier Science Inc. All rights reserved.