Experimentally characterized ligands are typically classified according to their denticity (i.e., number of distinct electron-donating groups) and hapticity (i.e., number of electron-donating atoms in a continuous series). However, such distinctions become difficult to maintain with respect to TMC connectivity processed from recorded structures (i.e., in mol2 files) in the CSD. In a connectivity record associated with a structure file, the bonds act as proxies for spatial relationships rather than as descriptions of the nature of the chemical bond. Because our goal is to accurately predict metal-ligand coordination and generate 3D structures of the resulting TMCs, we opt to classify ligands by the total number and identity of coordinating atoms, avoiding the distinction between denticity and hapticity. We also required that the ligand consist of more than one atom (Figure and SI Appendix, Table ). The decision to include only ligands with up to six coordinating atoms was motivated by the observation that ligands with seven or more coordinating atoms were extremely rare in the dataset: at the point of applying the filter on the number of coordinating atoms, only 337 ligands with seven or greater coordinating atoms were removed (SI Appendix, Table ). Finally, we only retained ligands for which a valid and unique SMILES could be written by RDKit, 75 where failures were typically due to kekulization failure in aromatic systems (see Methods and SI Appendix, Table ). Hemilabile ligands exhibiting multiple unique coordination modes were removed to ensure the dataset contains only ligands of unambiguous coordination that also do not exhibit coordination preferences that depend on metal identity.