In summary, we mapped the chemical space of over 230,000 crystallized TMCs and highlighted areas for future effort. Across mononuclear TMCs, we found that 3p coordinating ligands and 4d and 5d transition metals are systematically undersampled. We observed that tetradentate ligands are studied in various geometries and are frequently promiscuous, supporting many metals. We quantified the pocket size of the most promiscuous ligand, tetraphenylporphyrin, and identified over 1,500 ligands that are likely to be similarly promiscuous, although they have not been crystallized with many metals indicating potential for TMC synthesis opportunities. By analyzing tetradentate ligand connectivity and metal coordination geometry, we found that whether the ligand forms a closed ring through all metal-coordinating atoms does not dictate the metal coordination geometry that it is crystallized in, whereas the nature of coordinating atoms in ring substructures (e.g., N in pyrrole vs. N in an amine) holds a greater influence. After identifying ligands that are observed in the presence and absence of likely labile monodentate ligands, we identified whether some of these ligands could be useful, untapped catalysts. We identified an example of an octa-functionalized porphyrin that does not have documented use for catalysis but is a promising candidate for coordinating multiple metals. Further analysis of compounds in the CSD in additional coordination geometries is expected to present other opportunities for repurposing synthesized TMCs in future experimental and computational studies.