Regioselective hydrogenation of alkenes over atomically dispersed Pd sites on NHC-stabilized bimetallic nanoclusters

Summary

A catalyst containing atomically dispersed Pd sites on N-heterocyclic carbene (NHC)-stabilized Au nanoclusters, with the precise formula of PdAu₉(NHC^Bn)₇X₂ (NHC^Bn is dibenzylbenzimidazolin-2-ylidene, X is Br or Cl), has been developed for the regioselective hydrogenation of alkenes. Each Pd site is encircled by an Au₉ ring protected by seven NHC and two halide ligands. Such an encirclement arrangement and open stereochemical framework endow the single Pd atom with the power to activate molecular hydrogen and catalyze the hydrogenation of alkenes efficiently. Interestingly, it otherwise exhibits much lower activity toward the crowded alkenes, owing to the inherent and highly stringent steric requirement of NHC ligands, as also visualized by the theory. As such, these clusters are demonstrated to be a highly efficient (653 h⁻¹ of turnover frequency) and highly selective (97%) catalyst in the regioselective hydrogenation of linalool, an important synthetic perfume and a key intermediate in the synthesis of vitamin A.