For instance, we find that a Zr complex (refcode: MITZEW) with an N-and O-coordinating tetradentate ligand has bond lengths that are likely to support an isovalent series of group 8 metals (e.g., Fe, Ru, Os), which do not appear in the CSD in complex with that macrocycle (Figure and Supporting Information Table ). In contrast, we find a V complex (refcode: KARRAX) with a smaller pocket size that can likely support Fe but is too small to support Ru or Os (Figure and Supporting Information Table ). In an octahedral coordination environment, the tetradentate ligand must be combined with either two monodentate ligands, or in a minority of cases a bidentate ligand, to complete metal coordination. As described earlier, a significant number of complexes in the CSD were observed to have tetradentate ligands in combination with two monodentate ligands. To further identify if these complexes have a labile monodentate ligand making them amenable to catalysis, we inspected the monodentate ligands that are paired with tetradentate ligands (Supporting Information Figure ). The most common monodentate ligands include anions (e.g., chloride and bromide) and neutral small molecules (e.g., methanol and acetonitrile) that are common solvents and thus are likely labile (Supporting Information Figure ). We curated a list of likely labile ligands corresponding to solvents and find that 34% (1,429 out of 4,255) of unique tetradentate ligands in an octahedral geometry are paired with a labile solvent monodentate ligand (Supporting Information Table ).