The formation and reaction mechanism of polynuclear copper hydrides remain unstudied since their first synthesis in the late 80s. This is due to the myriad of potential active species that can arise from aggregation and fragmentation of Cu. Carrying out mechanistic studies requires structural information on the intermediate complexes, clusters and particles. EXAFS is a suitable method to resolve complex reaction mixtures, and spectroscopic simulation on realistic models can assist the interpretation of the data. We will identify the key reaction intermediates in the formation and reactivity of copper-hydride cluster-catalyzed reductions using multivariate-resolved HERFD-EXAFS assisted by spectroscopic simulation on a library of potential intermediates sampled computationally through DFT-MD.