Non-covalent interactions of 7th group and tetrahedral anions

A targeted survey of structural databases, particularly focusing on salts of organic perrhenates, pertechnetates, and permanganates reveals that these tetrahedral anions (MO₄) form a variety of notable supramolecular synthons. These anions can assume diverse roles within the crystal structures. This review provides a detailed analysis of known organic and some selected inorganic salts and complexes containing such tetrahedral anions, identifying several previously overlooked subtypes of suprastructures. These suprastructures are classified into four categories based on their non-covalent contacts: clusters, polymers, networks, and framework. Our analysis demonstrates that tetrahedral anions are capable of forming 55 distinct structural motifs through non-covalent interactions in both organic and inorganic crystals, which can be categorized into 24 types of bonding interactions. We introduce the concept of denticity of the tetrahedron and its central atom within superstructures. Additionally, a brief statistical analysis of anion–anion non-covalent interactions in compounds of the manganese subgroup is presented.