Organometallic and Radical Chemistry of B12 Coenzymes

  • Bernhard Kräutler
Chapter
Part of the NATO ASI Series book series (ASIC, volume 257)

Abstract

Vitamin B12-derivatives act as organometallic catalysts in nature and as one-electron redox centers. Besides their participation in the complex coenzyme B12-catalyzed enzymatic isomerization reactions, an essential biological role of the corrinoids also is methyl group transfer catalysis. Methyl group transfer reactions between corrinoid cobalt complexes were now found to take place with ease in aqueous solution and at room temperature, and the corresponding equilibria were studied. In this way, the thermodynamic effect of the intramolecular coordination of the unique nucleotide function of the cobalamins on the Co-C bond was studied. Secondly, the structure of a paramagnetic Co(II)corrin was analyzed by X-ray analysis. When compared with the corresponding diamagnetic Co(III)corrin precursor, the cobalt corrin portions were found to be highly similar, geometrically. This X-ray analysis points to the existence of a long axial bond in Co(II)corrins, but fails to reveal a deformation of the cobalt-corrin part that might represent a mode of activation of the protein bound coenzyme B12 towards Co-C bond homolysis.

Keywords

Bond Dissociation Energy Axial Bond Methyl Group Transfer Intramolecular Coordination Methyl Group Transfer Reaction 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • Bernhard Kräutler
    • 1
  1. 1.Laboratory of Organic Chemistry, ETH-ZürichZürichSwitzerland

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