Organoplatinum(II) and -palladium(II) Complexes of Nucleobases and Their Derivatives

The [(COD)M(R)] 14 VE complex fragments (COD = 1,5-cyclooctadiene, R = methyl or neopentyl (2,2-dimethylpropyl), M = Pd or Pt) bind to the nucleobases cytosine (Cyt) or uracil (Ura), to the methylated nucleobase derivatives 1-methylcytosine (1MeCyt) or 1-methyluracil (1MeUra), and to the related ligand caffeine (Caf) (1,3,7-trimethylxanthine). From the potentially bridging cytosinate ligand a binuclear platinum complex [(COD)(Me)Pt(N3-cytosinate-N1)Pt(Me)-(COD)](+) was obtained. The solubility of the corresponding complexes in organic solvents allowed their characterization by multiple (H-1, C-13, and Pt-195) NMR spectroscopy and in some cases by crystal structure analysis. Relative ligand-metal bond strength Were discussed in view of H-1-Pt-195 NMR coupling constants. Further focus lies on the observation of binding isomers, the formation of binuclear species, multiple Substitution, and the observed differences between Pt and Pd derivatives. Cytotoxicity experiments on HT-29 colon carcinoma and MCF-7 breast cancer cell lines revealed promising activities for selected platinum COD complexes.