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Updated: Jul 25, 2025

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry
Published on: February 4, 2017
Binding Small Molecules to a cis-Dicarbonyl 99TcI-PNP Complex via Metal-Ligand Cooperativity
Manuel Luca Besmer1, Henrik Braband1, Thomas Fox1
1Department of Chemistry, University of Zurich, Zurich CH-8057, Switzerland.
Abstract:
Metal-ligand cooperativity is a powerful tool for the activation of various bonds but has rarely, if ever, been studied with the radioactive transition metal 99Tc. In this work, we explore this bond activation pathway with the dearomatized PNP complex cis-[99TcI(PyrPNP*)(CO)2] (4), which was synthesized by deprotonation of trans-[99TcI(PyrPNP)(CO)2Cl] with KOBu. Analogous to its rhenium congener, the dearomatized compound reacts with CO2 to form the carboxy complex cis-[99TcI(PyrPNP-COO)(CO)2] and with H2 to form the mono-hydride complex cis-[99TcI(PyrPNP)(CO)2H] (7). Substrates with weakly acidic protons are deprotonated by the Brønsted basic pincer backbone of 4, yielding a variety of intriguing complexes. Reactions with terminal alkynes enable the isolation of acetylide complexes. The deprotonation of an imidazolium salt results in the in situ formation and coordination of a carbene ligand. Furthermore, a study with heterocyclic substrates allowed for the isolation of pyrrolide and pyrazolide complexes, which is uncommon for Tc. The spectroscopic analyses and their solid-state structures are reported.
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