N-Heterocyclic Carbene-Stabilized Hydrido Au 24 Nanoclusters: Synthesis, Structure, and Electrocatalytic Reduction of CO 2 .

Atomically precise hydrido gold nanoclusters are extremely rare but interesting due to their potential applications in catalysis. By optimization of molecular precursors, we have prepared an unprecedented N-heterocyclic carbene-stabilized hydrido gold nanocluster, [Au ₂₄ (NHC) ₁₄ Cl ₂ H ₃ ] ³⁺ . This cluster comprises a dimer of two Au ₁₂ kernels, each adopting an icosahedral shape with one missing vertex. The two kernels are joined through triangular faces, which are capped with a total of three hydrides. The hydrides are detected by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy, with density functional theory calculations supporting their position bridging the six uncoordinated gold sites. The reactivity of this Au ₂₄ H ₃ cluster in the electrocatalytic reduction of CO ₂ is demonstrated and benchmarked against related catalysts.