The structure-function relationship between dynamics and reactivity remains a tendentious topic in the protein (and metalloenzyme) literature; however, quantitative and atomistic models for systematically correlating dynamics with reactivity remain elusive. Herein, we report the relationship between dynamics and reactivity in the context of small-molecule biomimetic complexes of [Fe]-Hydrogenase by utilizing anthracene and thianthrene as rigid and flexible ligand scaffolds, respectively. Kinetic analysis of the rigid and dynamic complexes toward H2/D2 activation and subsequent hydride/deuteride transfer demonstrate that incorporation of a flexible ligand scaffold enhances reaction rates by ~5×. Eyring analysis revealed that the dynamic system exhibited a greatly decreased ΔH‡ contribution to the transition state barrier, while the ΔS‡ contribution exhibited a small but important increase — consistent with a greater need to organize the transition state structure in the dynamic case. Kinetic isotope studies (using D2) revealed an inverse KIE, indicating hydride transfer to the acridinium substrate as the rate limiting step. Computationally, DFT and CREST calculations suggest the dynamic complex can access a greater variety of geometric configurations. The results herein suggest that dynamics is an important design consideration to be added to the canonical list of drivers of reactivity.