In order to test the limits of this encouraging performance, we carried out a more stringent test of a grouped split in which we nearly eliminated specific coordinating atom elements from the training set. Specifically, we removed 90% of the ligands that contained at least one phosphorus atom as a coordinating atom from the entire dataset and defined a new test set that only contained ligands with at least one phosphorus atom as a coordinating atom. This split largely preserves our label balance (i.e., 51:49 hemilabile:non-hemilabile in training and 45:55 in the test set). Although performance is expectedly reduced, this model still shows encouragingly good performance, including an ROC-AUC of 0.94, accuracy of 0.87, and a recall of 0.84 (Supporting Information Figures S15-S17 and Table ).