σ-Hole Interactions Involving a Group 7 Metal: Close Contacts in Neutral and Anionic Rhenium Derivatives

Some cases of close contacts involving rhenium of perrhenate esters are presented and investigated computationally. The structures and calculated interaction energies confirm the attractiveness of these contacts, which display geometries typical of sigma-hole interactions. The short Re center dot center dot center dot O contacts observed in three crystalline perrhenate salts confirm the general ability of rhenium compounds, both neutral and ionic, to form such interactions.