Intramolecular Matere Bonds in Isostructural Rubidium (18‐Crown‐6) Pertechnetate and Perrhenate Dimers

The synthesis and structural characterisation of isostructural [Rb(18‐crown‐6)][XO 4 ] (X = Tc, Re) confirm a dimeric structure, [Rb(18‐crown‐6)] 2 [XO 4 ] 2 . X‐ray diffraction analysis reveals that the dimers feature a [Rb 2 X 2 O 8 ] core formed by two macrocycle‐bound Rb + cations bridged by XO 4 – . Their arrangements are directed by Rb–O coordination and by two equivalent X···O Matere bonds (MaBs). Unlike previously reported MaBs that link these oxoanions into extended supramolecular polymers or layers, the interactions described here occur within the discrete dimeric cluster, representing the first such examples of intramolecular MaBs for pertechnetate and perrhenate. Computational analysis clarifies the origin of these contacts. Molecular electrostatic potential maps reveal σ‐holes at Tc and Re, supporting MaB formation. Quantum theory of atoms in molecules, noncovalent interaction plots, and natural bond orbital calculations independently confirm the presence and stabilising nature of the X···O interactions. These results highlight the role of σ‐hole interactions in determining the solid‐state architecture of pertechnetate and perrhenate crown‐ether complexes and provide insight relevant to oxoanion behaviour in separation processes and nuclear waste management.