Multinuclear magnetic resonance studies of the reactions of the antitumor complexes cis-Pt(L)2X2 and cis-Pt(NH3)(L)X2 (L = cyclobutylamine and cyclopentylamine) with guanosine and other bases and crystal structures of Pt(cyclopentylamine)2I2

The crystal structures of two Pt(cyclopentylamine)2I2 compounds were determined by X-ray diffraction methods. Both crystals contain disordered cyclopentylamine ligands. Crystal I contains two independent trans-Pt(cyclopentylamine)2I2 molecules and all the C atoms are disordered on two positions. The second crystal (II) is most interesting since it contains both cis- and trans-Pt(cyclopentylamine)2I2 isomers in the same unit cell. It was prepared from the recrystallization of the cis isomer in acetone. The C atoms of the trans molecule in crystal II are disordered on two positions, while only one position was determined in the cis molecule, although some of the C thermal factors are quite high. The reactions of cis-Pt(amine)2X2 and cis-Pt(NH3)(amine)X2 (amine = cyclobutylamine and cyclopentylamine) with guanosine in water were studied in different Pt:guanosine proportions by multinuclear (1H, 195Pt and 15N) magnetic resonance spectroscopy. The presence of several species in solution was observed. For the mixed-cyclobutylamine compound, 15N NMR has shown that some of the NH3 ligands have been displaced from the coordination sphere in the presence of an excess of guanosine. The reactions of the two mixed-ligand complexes cis-Pt(NH3)(amine)Cl2 with 9-methylguanine, inosine and 9-methylhypoxanthine were also studied in water and the results are discussed.