METHYLATION OF PLATINUM COMPLEXES BY METHYLCOBALAMIN

The biomethylation reaction between platinum and methylcobalamin (MeB12) has been shown to involve both Pt(II) and Pt(IV) oxidation states. Kinetic, equilibrium, and 270-MHz 1H NMR studies have been used to show that an “outer-sphere” complex is formed between charged Pt(II) salts and the corrin macrocycle, which catalytically labilizes the Co-C σ bond to electrophilic attack. This research provides us with the first example of “activation” of the Co-C σ bond of MeB12through the interaction of a charged species with the corrin macrocycle. The significance of this discovery is discussed in terms of the reactions catalyzed by B12enzymes. © 1979, American Chemical Society. All rights reserved.