To Sandwich Technetium: Highly Functionalized Bis‐Arene Complexes [^99mTc(η⁶‐arene)₂]⁺ Directly from Water and [^99mTcO₄]⁻

Abstract

The labeling of (bio)molecules with metallic radionuclides such as ^99m Tc demands conjugated, multidentate chelators. However, this is not always necessary since phenyl rings can directly serve as integrated, organometallic ligands. Bis-arene sandwich complexes are generally prepared by the Fischer-Hafner reaction. In extension of this, we show that [^99m Tc(η⁶ -C₆ R₆ )₂ ]⁺ -type complexes are directly accessible from water and [^99m TcO₄ ]^- , even using arenes incompatible with Fischer-Hafner conditions. To unambiguously confirm the nature of these unprecedented ^99m Tc complexes, their rhenium homologous have been prepared by substituting naphthalene ligands in [Re(η⁶ -C₁₀ H₈ )₂ ]⁺ with the corresponding phenyl groups. The ease with which highly stable [^99m Tc(η⁶ -C₆ R₆ )₂ ]⁺ complexes are formed under standard labeling conditions enables a multitude of new potential imaging agents based on commercial pharmaceuticals or lead structures.