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

Treatment of [Ni₂₃Se₁₂Cl₃(PEt₃)₁₀] (1-Cl) with excess Me₃SiX (X = Br, I) results in formation of [Ni₂₃Se₁₂X₃(PEt₃)₁₀] (X = Br, 1-Br; X = I, 1-I) in good yields. 1-Br and 1-I are exceptionally rare examples of atomically precise nickel nanoclusters (APNCs). Both 1-Br and 1-I 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 1-Br 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] (2-I) 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.