Atomically Precise NHC-Protected Alkylgold Nanoclusters

Alkylgold complexes are of paramount significance in organometallic chemistry owing to their catalytic relevance, yet atomically precise alkylgold(0) species remain unexplored. Herein, we report the first structurally authenticated alkyl-ligated Au(0) nanocluster, [Au₆₄(NHC^{i Pr})₁₄Et₁₀Cl₆](BF₄)₂ (Au₆₄, NHC^{i Pr} = 1,3-diisopropylimidazolin-2-ylidene, Et = ethyl), synthesized via a facile base-mediated alkylation strategy with alkylboronic acids as precursors. X-ray crystallography reveals a box-shaped Au₁₆@Au₄₀@Au₈ architecture with near D_{4 h} symmetry, bearing 14 NHC ligands on the longitudinal plane and 10 alkyl ligands at both ends, all bound in a terminal coordination mode. DFT calculations demonstrate that ethyl→Au σ-donation dominates the orbital interaction, accompanied by partial negative charge accumulation on the alkyl carbons. Although the weak nucleophilicity associated with ethyl groups, protonation of the Au-ethyl bond is thermodynamically favored, and C(sp³)-C(sp³) cross-coupling readily available with strong electrophiles. Notably, β-hydride elimination of ethyl moieties is directly observed under alkaline conditions, providing the first experimental evidence for this critical transformation at Au(0) centers. This work not only establishes an efficient synthetic route to alkyl-functionalized gold NCs but also delivers comprehensive insights into the fundamental reactivity and transformation of alkyl-gold(0) species.