The proposed quasi elastic neutron scattering experiment at ISIS aims at the characterization of the dynamical properties of the series of coordination complexes Pr(BH4)3·nNH3, n = 4 – 7. The systematic variation in the number of ligands triggers changes from ionic to molecular structures which in turn influences decisively dihydrogen interaction between partly positively charged hydrogen bonded to N and partly negatively charged hydrogen bonded to B. Our goal is to determine the mechanistic aspects (i.e. spatial geometry, time-scale, activation energy) of the reorientational dynamics of the BH4 and NH3 moieties, as well to determine how they depends on n.