After these two phases of training, we tested the accuracy and stability of the resulting potential by comparing the MLP energies and forces with the ground truth data (for details see SI §S2) and conservation of the total energy in NVE dynamics. Despite the high accuracy of the trained ACE potential, as evidenced by a mean absolute deviation (MAD) of 0.79 meV/atom for energy and 46 meV Å-1 for forces (Fig. ), the NVE and NVT MD simulations using PBC with the ACE potential were unstable. This included the formation of bubbles, followed by the system's collapse. These instabilities could be alleviated by introducing more radial functions into the descriptor and tuning the hyperparameters. How- (iii) The [Pd(MeCN) 4 ] 2+ •MeCN complex solvated by 20 to 30 MeCN molecules to describe interactions between Pd and MeCN (251 structures). As in the Mg 2+ case, the size of all clusters was selected in a way that the resulting cluster radius exceeds the 6 Å cut-off used in ACE and MACE descriptors. Unless specified otherwise, ACE was used as the ML model in all training phases, employing the ground truth potential TPSS0-D3BJ/def2-TZVP, since this functional has shown good performance in reactions involving latetransition metals. MD simulations in the AL loops were performed in an NVT ensemble at 300 K. MD simulations longer than 1 ps used a flat-bottom spherical harmonic bias potential set at a distance from the Pd 2+ cation, applying a harmonic restraint of 100 kcal/mol Å-2 .