DINUCLEAR NUCLEOBASE-ANION-BRIDGED COMPLEXES OF PD-II AND PT-II WITH 1-METHYLIMIDAZOL-2-YL PYRIDIN-2-YL KETONE - SYNTHESIS, CRYSTAL-STRUCTURE AND SOLUTION BEHAVIOR

The reactions of [M(mipk)(H2O)(2)](2+) (M = Pd or Pt; mipk = 1-methyli midazol-2-yl pyridin-2-yl ketone) with the nucleobases 1-methylthymine (Hmthy) and 1-methyluracil (Hmura) were studied and the products char acterized by X-ray structure analyses as well as by H-1 NMR spectrosco py. Dinuclear complexes are formed with the pyrimidine-based model nuc leobases, which act as secondary bridging ligands via their N-3 and O- 4 donor functions. In all three compounds [Pd-2(mipk)(2)(mura)(2)][ClO 4](2) 1, [Pd-2(mipk)(2)(mthy)(2)][ClO4](2) 2 and the isotypic compound [Pt-2(mipk)(2)(mthy)(2)][ClO4](2) 3 the nucleo bases show head-to-tai l arrangement. The intramolecular M ... M distances vary from 2.861(1) Angstrom in 2 to 2.879(1) Angstrom in 1. By ligand exchange reaction in aqueous media the side product [Pt(mipk)(2)][ClO4](2) is formed. Pr oton NMR studies showed that the dinuclear complexes are not stable in aqueous solution. Oxidation of 3 and [Pt-2(mipk)(2)(mura)(2)][ClO4](2 ) 4 to platinum blues with higher-valent Pt was not observed. Presumab ly this is due to the competing oxidation of the low-potential mipk li gand.