Multinuclear NMR Studies of Ligand-Exchange Reactions on Analogous Technetium(V) and Rhenium(V) Complexes. Relevance to nuclear medicine
✍ Scribed by Lothar Helm; Karen Deutsch; Edward A. Deutsch; André E. Merbach
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- German
- Weight
- 468 KB
- Volume
- 75
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
The kinetics of pyridine exchange on truns-[MO,(py),]' have been followed by 'H-NMR in CD,NO, for M = Re, Tc: k298/s-' = (5.5 i 0.1) x 0.04 i 0.02; A H #/kJmol-' = 11 1 f-3, 101 f 9; dSf/JK-'mol-' = +28 * 10, +68 * 35. For the ReV complex, pyridine and oxygen exchanges have been measured simultaneously by 'Hand I70-NMR in deuterated water: k298/s-1 = (8.6 i 0.2) x (oxygen);
For both complexes, the rate law for pyridine exchange is first-order in complex and zero-order in pyridine; together with the activation parameter values, and the fact that the rate does not depend significantly on the nature of the solvent, this strongly implies the operation of a dissociative mechanism. The ratio of pyridine exchange rates for the Tc and Re complexes at room temperature is ca. 8000. The consequences of these observations for radiopharmaceutical synthesis are discussed.
(py), (14.5 0.3)