Donor atom preferences in complexes of platinum and palladium with amino acids and related molecules

Amino acids present metal ions with a choice of potential donor atoms. The preferences for a particular donor atom for palladium(II) depends primarily on relative thermodynamic stabilities of the complexes formed, but for platinum thermodynamically less preferred complexes may be kinetically preferred, leading often to spontaneous conversion of a metastable complex into a thermodynamically preferred linkage isomer. Sizes of potential chelate rings often play a crucial role in determining donor atom preferences. On a more subtle level, when geometric isomers are possible with the same set of donor atoms bound to the metal, there may frequently be thermodynamic or kinetic preferences for a particular isomer depending on trans influences and trans effects of other ligands. These preferences are most marked when the trans influences of some of these ligands are very high, as in methylplatinum(IV) complexes. The review focuses on results obtained in the author's laboratory, and on related work of other groups. (C) 1997 Elsevier Science S.A.