From Tc^VII to Tc^I; facile syntheses of bis-arene complexes [^99(m)Tc(arene)₂]⁺ from pertechnetate

Abstract

Bis-arene complexes of technetium represent a fundamental class of organometallic compounds. Due to complex synthetic routes, no detailed insights into their properties have been reported so far. Reacting [⁹⁹TcO₄]^- with arenes in the exclusive presence of AlCl₃ gives highly stable [⁹⁹Tc(arene)₂]⁺ in good yields. These complexes have extraordinarily high stabilities, where oxidation is found to occur at potentials higher than +1.3 V and reduction at potentials below -2 V <i>vs.</i> Fc/Fc⁺. The ^99mTc analogues are similarly synthesised by applying a novel ionic liquid extraction pathway. Complexes of ^99mTc with suitably functionalized arenes will represent new building blocks for bioorganometallic pharmaceuticals in molecular imaging.