The structures of the salts and the different models of the catalysts under study were optimised at the wB97x-D/def2-tzvp computational level and the real catalysts were optimised at wB97x-D/def2-svp. Harmonic frequencies were computed at the optimisation level to confirm that the relaxed structures correspond to local minima. In some structures, marked with * , the distance N -H was fixed to avoid H transfer and to keep all complexes consistent for analysis. Single-point calculations were performed to improve the energy description at the computational level of wB97x-D/def2-qzvp for salts and models and wB97x-D/def2-tzvp computational level for the real catalysts under study. Structure optimisations and energy calculations were performed using the Gaussian16 software. All the calculations were performed in the gas phase and at room temperature (298K). The optimised structures can be found in Table .