ELECTROCHEMISTRY OF BORON-CAPPED TC-99 DIOXIME COMPLEXES

Boron-capped technetium dioxime (BATO) compounds (1) have been studied by cyclic voltammetry, d.c. polarography, and controlled-potential coulometry/bulk electrolysis in DMF. Chloro and bromo BATOs undergo an irreversible two-electron reduction at mercury while for hydroxy BATOs two consecutive one-electron reductions are observed. Rhenium analogs to the BATOs exhibit qualitatively similar reduction behaviour, but at more negative potentials. The uncapped tris-dioxime complexes (2) also show similar electrochemical behaviour. The two-electron peak potential is more sensitive to changes in the axial ligand and the dioxime than to changes in substituents on the boronic acid capping group. BATO reduction apparently leads to axial ligand loss and yields an air-sensitive, purple species. Both BATO reduction and oxidation appear to be biologically inaccessible.