We used AtomAccess to determine the size of equatorial binding sites in 290 dysprosium metallocene and derivatized metallocene fragments (Table ) using atomic coordinates extracted from the Cambridge Structural Database (CSD; see ESI for details). Figure shows how AtomAccess can identify the propensity of a dysprosocenium fragment to allow equatorial coordination in a particular geometry. Isolated dysprosocenium cations have a maximum cluster size of 7.1% SA and a mean largest cluster size of 3.2% SA, reflecting the highly sterically hindered geometries. Fragments with a single equatorial coordination site, n = 1, have binding sites of 14.5-20.4% SA, enabling the coordination of a single halide (Cl, Br, I) or borohydride ligand; these compounds are often used as precursors to isolated dysprosocenium cations. Dysprosocenium fragments that allow the coordination of multiple ligands or multi-dentate ligands (n ≥ 2) have a minimum largest cluster of 20.8% SA. Hence, the threshold for single equatorial interactions from this dataset is between 7.1 and 14.5% SA, and ~20.5% SA is the threshold for multiple equatorial interactions.