Transition metal hydrides are critically involved in many stoichiometric and catalytic organometallic reactions, such as hydrogenation. In these reactions a crucial step is the coordination of an intact H2 molecule to the metal centre and the ligand dynamics of the resulting coordination compound. We propose to investigate the temperature dependence of the Anisotropic Displacement Parameters obtained from multi-temperature single-crystal neutron diffraction on the octahedral complex trans-(P iPr3)2IrIH2(H2), in order to get valuable insight on the motion of the hydrogen atoms attached to the metal and consequently on the nature of the H/H2 exchange process and the H2 absorption/desorption process.