MgO-Supported Iridium Metal Pair-Site Catalysts Are More Active and Resistant to CO Poisoning than Analogous Single-Site Catalysts for Ethylene Hydrogenation and Hydrogen-Deuterium Exchange

Atomically dispersed supported catalysts are drawing wide attention because they offer properties different from those of conventional catalysts, with maximally efficient use of the metals. However, the performance of single-site catalysts is often limited by the lack of neighboring metal centers to cooperate in catalysis. Thus, there is motivation to extend this class to catalysts incorporating isolated metal pairs. We report pairs of iridium atoms on MgO initially stabilized by support oxygen and cyclooctadiene ligands and activated by the removal of the latter. These catalysts are stable in a range of environments, including CO, H-2, and C2H4 + H-2 at 298-353 K and are more active than analogous single-site catalysts in ethylene hydrogenation and hydrogen deuterium exchange because the neighboring metal centers facilitate hydrogen activation. Moreover, the pair-site catalysts retain activity even in the presence of CO, which poisons the single-site analogues. Supported metal pair-site catalysts open pathways toward understanding and applications of supported molecular catalysts.