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 -2Vvs. 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.