Synthesis of [Ni₂₃Se₁₂X₃(PEt₃)₁₀] (X = Br, I) via Post-synthetic Modification

Treatment of [Ni₂₃Se₁₂Cl₃(PEt₃)₁₀] (<b>1-Cl</b>) with excess Me₃SiX (X = Br, I) results in formation of [Ni₂₃Se₁₂X₃(PEt₃)₁₀] (X = Br, <b>1-Br</b>; X = I, <b>1-I</b>) in good yields. <b>1-Br</b> and <b>1-I</b> are exceptionally rare examples of atomically precise nickel nanoclusters (APNCs). Both <b>1-Br</b> and <b>1-I</b> were characterized by X-ray crystallography, NMR spectroscopy, and ESI-mass spectrometry. Both clusters feature a compact [Ni₁₃]⁷⁺ kernel capped by a [Ni₁₀(μ-Se)₉X₃]^- shell. Cluster <b>1-Br</b> could also be isolated cleanly using a bottom-up synthetic approach, via reaction of [Ni(1,5-cod)₂] and PEt₃ with SePEt₃ and [NiBr₂(PEt₃)₂]. Under these conditions, it could be isolated in 43% yield. In contrast, reaction of [Ni(1,5-cod)₂] and PEt₃ with SePEt₃ and [NiI₂(PEt₃)₂] results in formation of [Ni₃(μ₃-Se)₂I₂(PEt₃)₄] (<b>2-I</b>) as the only isolable product. These results highlight the challenges inherent in the bottom-up synthesis of Ni nanoclusters, and demonstrate the value of postsynthetic modification in the synthesis of 3d metal APNCs.