The syntheses of high oxidation state metal complexes containing the tripodal ligand [(η5-C5H5)Co{P(OMe)2(O)}3]− and the X-ray crystal structure of [(η5-C5H5)Co{P(OMe)2(O)}3 ReO3]

Activation of [(99(m))TcO4](-) by phosphonium cations

Phosphonium salts in solution or bound to solid phase supports interact with the robust [(99(m))TcO4](-) anion in neutral water. This activated form of [(99(m))TcO4](-) represents a source for complexes with the fac-{(99m)Tc(VII)O3}(+) core, which can be synthesized in high yields and purity.

fac-[TcO3(tacn)]+: a versatile precursor for the labelling of pharmacophores, amino acids and carbohydrates through a new ligand-centred labelling strategy

Herein, we report a protocol for the synthesis of [(99m)TcO(3)(tacn)](+) ([1](+)) (tacn = 1,4,7-triazacyclononane) that is suitable for clinical translation. Bioconjugates containing pharmacophores ([TcO(NO(2)-Imi)(tacn)](+); [3](+)), artificial amino acids ([TcO(Fmoc-allyl-His)(tacn)](+); [5](+)), and glucose derivatives ([TcO(allyl-tetraacetylglucose)(tacn)](+); [7](+)) were synthesized by cycloaddition strategies and fully characterized ((99)Tc and (99m)Tc). These new technetium complexes are stable at neutral pH and demonstrate the potential and flexibility of the [3+2] cycloaddition labelling concept. In addition to the synthetic work, the first biodistribution studies of [1](+) and the small [3+2] cycloadduct [(99m)TcO(NO(2)-Imi)(tacn)](+) ([3](+)) were completed. The biodistribution studies suggest the stability of these complexes in vivo. Furthermore, it was demonstrated that the high hydrophilicity of the [(99m)TcO(3)(tacn)](+) building block is a complement to the complexes of the fac-{Tc(CO)(3)}(+) core.

High-valent technetium complexes with the [(99)TcO(3)](+) core from in situ prepared mixed anhydrides of [(99)TcO(4)](-) and their reactivities

The highly reactive mixed anhydrides [TcO3(OCOPh)] and [TcO3(OBF3)]- were synthesized by treatment of [TcO4]- with strong Lewis acids benzoyl chloride and BF3.OEt2. These mixed anhydrides, prepared in situ, were used as precursors for the synthesis of complexes containing the [TcO3]+ core. Subsequent reactions with bi- or tridentate ligands resulted in new complexes comprised of the [TcO3]+ core. As examples with bidentate ligands, the classical complexes [TcO3Cl(bipy)] (1) (bipy = 2,2'-bipyridine) and [TcO3Cl(phen)] (2) (phen = 1,10-phenanthroline) have been prepared by this strategy and structurally characterized. The new compounds [TcO3(bpza)] (3) (bpza = di-1H-pyrazol-1-ylacetate), [TcO3(bpza*)] (4) (bpza* = bis(3,5-dimethyl-1H-pyrazol-1-yl)acetate), [TcO3(tpzm*)]+ (6) (tpzm* = 1,1,1-methanetriyltris(3,5-dimethyl-1H-pyrazole), and [ReO3(tpzm*)][ReO4] (7) are examples of complexes with tripod ligands. The complexes have been structurally characterized, and their 99Tc NMR spectra have been recorded. As a common feature, the X-ray structures show a distinct widening of the O-Tc-O angles, almost to a tetrahedral angle. With the perspective of radiopharmaceutical applications, water stability and reactivities toward alkenes are described.