Multinuclear magnetic resonance studies of the reactions of the antitumor complexes cis-Pt(L) 2X 2 and cis-Pt(NH 3)(L)X 2 (L = cyclobutylamine and cyclopentylamine) with guanosine and other bases and crystal structures of Pt(cyclopentylamine) 2I 2

Abstract

The crystal structures of two Pt(cyclopentylamine) 2I 2 compounds were determined by X-ray diffraction methods. Both crystals contain disordered cyclopentylamine ligands. Crystal I contains two independent trans-Pt(cyclopentylamine) 2I 2 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) 2I 2 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) 2X 2 and cis-Pt(NH 3)(amine)X 2 (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 NH 3 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(NH 3)(amine)Cl 2 with 9-methylguanine, inosine and 9-methylhypoxanthine were also studied in water and the results are discussed.