Remarkably, hydrogen may be activated for chemical reaction at room temperature using a new family of frustrated Lewis acid-base pair (FLB) materials. In these complexes hydrogen is 'pinned' between the electron donating nitrogen and electron accepting boron atoms of the complex in a precursor complex before heterolytic cleavage of the hydrogen results in the formation of B-H and N-H hydrides. We have been using a combination of experiment and theory to understand how H2 is activated in FLB¿s. The stability of the hydrogen precursor complex is proportional to the Lewis acidity of the borane unit. Here we wish to characterize a FLB by inelastic neutron spectroscopy using the TOSCA spectrometer to follow the changes in the free-hydrogen rotational line as hydrogen becomes co-ordinated to the active site of the FLB.