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

The preparation of a series of novel Pt(IV) complexes containing the anioni c polyfluoroaryl ligands, 2,3,5,6-tetrafluorophenyl (p-HC6F4), 2,3,5,6-tetr afluoro-4-methoxyphenyl (p-MeOC6F4) and pentafluorophenyl (C6F5) are descri bed. The crystal structure of a representative complex, [Pt(p-MeOC6F4)(2)(O 2CEt)(2)(en)] (en = ethane-1,2-diamine) was determined and confirms the tra ns arrangement of the carboxylato ligands. Reduction potentials of the seri es of complexes reveal that replacement of equatorial chloro ligands by pol yfluoroaryl ligands makes reduction substantially more difficult. They also confirm previously reported trends in that complexes having axial carboxyl ato ligands are more readily reduced than those having axial hydroxo ligand s. Reduction potentials and in vitro activities showed no obvious correlati ons. Moderate to high activity was observed for many complexes in the serie s, including some of those that were very difficult to reduce. (C) 1999 Els evier Science Inc. All rights reserved.