The characterization of complexes that act as catalysts for chemical transformations is an important feature in the development of new methods of use to a sustainable chemicals sector. We have developed new compounds (hydrides) of rhenium that acts as catalysts in organic chemical transformations, but have neither been able to determine the number of hydrogen atoms bound to the rhenium centre, nor their specific geometric orientation and interactions with other atoms. Unlike in X-ray diffraction, in which hydrogen atoms are nearly invisible, neutron diffraction studies would allow us to pinpoint these atoms in the overall structure with a high degree of accuracy. We would be able to build on these data to understand the bonding in this compound and to derive a whole mechanism for the catalytic reaction.