From a mechanistic point of view, the failure of the models to extrapolate is not very surprising as nickel catalysts can react through very different mechanistic pathways . In this perspective, we analyzed the importance of the different features used by the models to perform predictions on more focused subsets of the NiCOlit. All reactions belonging to the same coupling partner category were regrouped and a predictive model was trained on each of these subsets. Then the importance of the features used by the models to perform the predictions were analyzed and displayed Fig. . The differences between the models are striking. As an example, the model trained on the RMgX coupling partner is highly dependent on the ligand, the substrate and the molar ratios used while the couplings with RLi mainly depend on substrate characteristics. Considering that widely different features are used to predict yields on the different coupling partner categories, the poor generalizability of the models is not surprising. FIG. : Analysis of feature importance in predictive models trained on coupling partner category NiCOlit subsets. Each subset contains all the reactions belonging to a category of coupling partners.