Modifying the properties of platinum(IV) complexes in order to increase biological effectiveness

Abstract

The preparation of a series of novel Pt(IV) complexes containing the anionic polyfluoroaryl ligands, 2,3,5,6-tetrafluorophenyl ( p-HC 6F 4), 2,3,5,6-tetrafluoro-4-methoxyphenyl ( p-MeOC 6F 4) and pentafluorophenyl (C 6F 5) are described. The crystal structure of a representative complex, [Pt( p-MeOC 6F 4) 2(O 2CEt) 2(en)] (en=ethane-1,2-diamine) was determined and confirms the trans arrangement of the carboxylato ligands. Reduction potentials of the series of complexes reveal that replacement of equatorial chloro ligands by polyfluoroaryl ligands makes reduction substantially more difficult. They also confirm previously reported trends in that complexes having axial carboxylato ligands are more readily reduced than those having axial hydroxo ligands. Reduction potentials and in vitro activities showed no obvious correlations. Moderate to high activity was observed for many complexes in the series, including some of those that were very difficult to reduce.