Platinum chelate planar molecule

FIGURE 2.33 Schematic representation of two enantiomers of a platinum chelate planar molecule. 

Several other recent reviews contain material relevant to this section. An article by Blandamer and Burgess on the thermodynamics, kinetics, and mechanisms of solvation, solvolysis, and substitution in nonaqueous solvents contains a contribution on the controversial dissociative mechanism for isomerization of square-planar molecules. This is outlined in Section 5.5. A review of ligand substitution reactions at low-valency transition-metal centers contains sections on five-coordinate metal carbonyl complexes and on ML4 complexes (mainly tetrahedral configurations with L being a tertiary phosphine), as well as on acid- and base-catalyzed reactions. A review by Constable " surveying the reactions of nucleophiles with complexes of chelating heterocyclic imines contains a sizable section on square-planar palladium and platinum derivatives. Most discussion centers on [Pt(bipy)2] and [Pt(phen)2] (bipy = 2,2 -bipyridine phen = 1,10-phenanthroline). The metal center, ligand, or both are susceptible to nucleophilic attack and the mechanisms involved are critically assessed. 

Cisplatin is a cancer-fighting drug that s a square planar platinum molecule (see Chapter 9). It s a relatively small molecule that binds to the backbone of a cancer cell s DNA. It kinks the structure of the DNA strand and prevents it from operating. The cisplatin binds to the DNA at two locations in effect, it acts as a multidentate ligand, or chelating complex (see Chapters 9 and 15 for more details). The chelating effect changes the symmetry of the DNA molecule. It s like cisplatin reaches out with two hands and pulls the DNA in such a way that it can t operate properly anymore. 

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