To curate a dataset of synthetically accessible ligands with known connectivity in TMCs, we queried the CSD for all entries containing a single transition metal atom in any coordination geometry with high resolution (see Methods). From this set, we used molecular graphs to identify 299,035 complexes with unique connectivity, and we extracted ligands from these complexes using molSimplify. This process resulted in a total of 95,385 unique ligands (SI Appendix, Table ). We filtered these unique ligands in several steps. In terms of elemental filters, we kept only those that consisted of atoms frequently present in organic ligands (i.e., H, B, C, N, O, F, Si, P, S, Cl, Br, I), and we required that the metal-coordinating atoms were common (i.e., C, N, O, Si, P, S, Figure and SI Appendix, Table ). We also restricted our ligands to those with between one and six total coordinating atoms as defined by the mol2 file representing each CSD entry.