Pt 4 and Pt 4 C 2 Pt, in the bulk or in the nanoparticle/cluster form, is a facile catalyst for ethane dehydrogenation, and Pt 4 is no exception to this, proving to bind ethane and activate C-H bonds with low activation barriers based on DFT calculations (vide supra). However, Pt suffers from lack of selectivity, and it has been shown both experimentally and computationally to dehydrogenate ethylene and acetylene, leading to rapid deactivation by coking. "Complete dehydrogenation" of ethane adsorbed on Pt 4 forms a Pt 4 C 2 cluster, which may be seen as the first step of coking. To assess theoretically the effects of this initial coking on catalytic activity and selectivity in subsequent reactions we must first explore the isomeric ensembles of Pt 4 and Pt 4 C 2 . Here we explore the initial coking product Pt 4 C 2 and directly compare it to Pt 4 GeC 2 , which is found to be selective and stable against further coking. Reactivity studies of fluxional systems are challenging because we must understand the contribution of each isomer to the overall reactivity. Using the Curtin-Hammet principle, where the distribution of products is determined by the free energy difference between the two transition states, ∆∆G ‡ , we consider the isomer with the lowest transition state energy relative to the global minimum the driver of reactivity for that step. To show this for our multi-component systems, we plot barriers on bar charts where all energies are given relative to the global minimum for that composition in Figure ). Therefore, accoridng to the Curtin-Hammet principle, the most reactive isomers are the ones with the lowest bar tops in Figure ). catalyst for ethane, with computed transition state energies as low as 0.29 eV above the ground state. When C 2 is added to the Pt 4 cluster, the barriers for ethane C-H activation increase to 0.64 eV, showing that a small amount of coke has a large deactivating effect.