Metal/Support Interactions Regulate Substrate Binding in Fe/Co/Se Cluster Catalysts.

Here, we investigate the stereoelectronic requirements of a family of Fe/Co 6 Se 8 molecular clusters to achieve a Goldilocks regime of substrate affinity for the catalytic coupling of tosyl azide and tert -butyl isocyanide. The reactivity of a catalytically competent iron-nitrenoid intermediate, observed in situ , is explored toward nitrene transfer and hydrogen-atom abstraction. The dual role of isocyanide, which, on the one hand, prevents catalyst degradation but, in large amounts, slows down reactivity, is exposed. The impact of distal changes (the number of neighboring active sites and the identity of supporting ligands) on the substrate affinity, electronic properties, and catalytic activity is investigated. Overall, the study reveals that the dynamic, push-pull interactions between the substrate ( t BuNC), active site (Fe), and support (Co 6 Se 8 ) create a regime where increased substrate activation occurs with facile dissociation.