However, reports of such reactivity are limited. Lu and co-workers have demonstrated isotopic scrambling of H2 + D2 mixtures to form HD using 1 st row transition metal complexes bearing Al, Ga or In based ligands. In this paper, we report a rare example of H2 activation using a transition metal complex supported by Mg-based ligands. We show that this reaction is reversible and leads to a palladium tetrahydride complex, featuring an unusual structural motif. Based on DFT calculations, a mechanism for H2 activation involving a ligand-assisted pathway is proposed.