Technetium Nitrido-Peroxo Complexes: An Unexplored Class of Coordination Compounds

Micol Pasquali,Adriano Duatti,Emilija Janevik-Ivanovska

doi:10.3390/inorganics7120142

Abstract

The purpose of this work was to further expand the chemistry of mixed technetium nitrido-peroxo complexes, a still poorly explored class of compounds containing the Tc(VII) moiety, [99gTc][Tc(N)(O2)2]. A number of novel complexes of the formula [99gTc][Tc(N)(O2)2(L)] with bidentate ligands (L) (where L = deprotonated alanine, glycine, proline) were prepared by reacting a solution of nitrido-technetic(VI) acid with L in the presence of a source of H2O2. Alternatively, the complex [99gTc][Tc(N)(O2)2X]− (X = Cl, Br) was used as a precursor for substitution reactions where the halogenide ion was replaced by the bidentate ligand. The new complexes were characterized by elemental analysis and mass spectroscopy. The preparation of the analogous [99mTc][Tc(N)(O2)2] moiety, radiolabeled with the metastable isomer Tc-99m, was also studied at a no-carrier-added level, using S-methyl-N-methyl-dithiocarbazate as the donor of the nitrido nitrogen atoms.

Highlights

The anionic technetium complex [99g Tc][Tc(N)(O2 )2 Cl]−, reported by Baldas and coworkers a few decades ago [1], was the first example of a transition compound containing a metal–nitrido multiple bond (M≡N) tethered to a peroxo (O2 2− ) group
The resulting metallic fragment exhibits an unexpectedly high stability in water, indicating that the nitrido nitrogen atom is effective in stabilizing the metal in its highest oxidation states, presumably because of its remarkable π-donor character
It was observed that the simple addition of the selected amino acid to a solution of the [99g Tc][Tc(N)(O2 )2 ] fragment elicited a reaction, it was difficult to isolate pure products from the reaction mixture

Summary

Introduction

The anionic technetium complex [99g Tc][Tc(N)(O2 ) Cl]− , reported by Baldas and coworkers a few decades ago [1], was the first example of a transition compound containing a metal–nitrido multiple bond (M≡N) tethered to a peroxo (O2 2− ) group. In this remarkable compound, the oxidation state of the technetium atom is +7 and the resulting coordination arrangement manifests high solubility and stability in aqueous solution. Several potential advantages could be envisaged by exploiting the distinctive chemical features of the [99g Tc][Tc(N)(O2 )2 ] fragment, in an aqueous solution

Objectives

Methods

Results

Discussion

Conclusion