We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Multinuclear NMR Studies of Ligand-Exchange Reactions on Analogous Technetium(V) and Rhenium(V) Complexes. Relevance to nuclear medicine.
- Authors
Helm, Lothar; Deutsch, Karen; Deutsch, Edward A.; Merbach, André E.
- Abstract
The kinetics of pyridine exchange on trans-[MO2(py)4]+ have been followed by 1H-NMR in CD3NO2 for M = Re, Tc: k298S−1 = (5.5 ± 0.1) × 10−6, 0.04 ± 0.02; Δ H≠/kJmol−1 = 111 ± 3, 101 ± 9; Δ S≠/JK−1mol−1 = +28 ± 10, +68 ± 35. For the Rev complex, pyridine and oxygen exchanges have been measured simultaneously by 1H- and 17O-NMR in deuterated water: k298/s−1 = (8.6 ± 0.2) × 10−6 (py), (14.5 ± 0.3) × 10−6 (oxygen); Δ H≠/kJmol−1 = 111 ± 1, 91 ± 1; Δ S /JK−1mol−1 = +32 ± 3, −32 ± 4. 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.
- Publication
Helvetica Chimica Acta, 1992, Vol 75, Issue 1, p210
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19920750119