Comparing PtII- and PdII-nucleobase coordination chemistry: Why PdII not always is a good substitute for PtII

As is well established, numerous similarities exist as far as reactivity patterns and structural features of the d8 metal ions M = Pd2+ and Pt2+ are concerned. Here reactions of metal complexes of type cis-[M(a)2X2] (a = NH3 or (a)2 = diamine or diimine; X = monodentate or X2 = bidentate leaving groups) with nucleobases, the constituents of nucleic acids, are discussed and differences regarding intrinsic stability of the starting compounds, kinetics of formation of products, thermodynamics of products, as well as donor site selectivity are pointed out. It is concluded that PdII complexes representing strict or close analogues of established antitumor PtII drugs of the Cisplatin-type, if active under in vivo conditions at all, are unlikely to have a similar mode of action as their PtII congeners. Relationships to supramolecular constructs containing cis-[M(a)2]2+ entities are likewise discussed.Peer reviewe