Structure and reactivities of rhenium and technetium bis-arene sandwich complexes [M(η6-arene)2]+

Abstract

Sandwich complexes are important building blocks in medicinal inorganic chemistry for group 6 and 8 elements but are almost unknown for the manganese triad. We present the syntheses and full characterization of the mixed-arene ⁹⁹Tc sandwich complexes [⁹⁹Tc(η⁶-hmbz)(η⁶-C₆H₅–NH₃)](PF₆)₂ and [⁹⁹Tc(η⁶-hmbz)(η⁶-C₆H₅–Br)](PF₆). Both comprise functionalities for conjugation to targeting molecules or for being included as substructures in pharmaceutically active lead compounds. Since η⁶-benzene ligands are too stably bound to be replaced with incoming ligands, we prepared naphthalene complexes [Re(η⁶-C₆H₆)(η⁶-napht)]⁺ and [Re(η⁶-napht)₂]⁺. Their reactivities towards substitution are increased and one or both naphthalene ligands can be replaced with mono- or multi-dentate ligands. Combining the features of ⁹⁹Tc and Re may lead to a molecule-based theranostic approach.