Understanding the Early Stages of Nickel Sulfide Nanocluster Growth: Isolation of Ni₃, Ni₄, Ni₅, and Ni₈ Intermediates

Abstract Addition of sub‐stoichiometric quantities of PEt₃ and diphenyl disulfide to a solution of [Ni(1,5‐cod)₂] generates a mixture of [Ni₃(SPh)₄(PEt₃)₃] (1), unreacted [Ni(1,5‐cod)₂], and [(1,5‐cod)Ni(PEt₃)₂], according to ¹H and ³¹P{¹H} NMR spectroscopic monitoring of the in situ reaction mixture. On standing, complex 1 converts into [Ni₄(S)(Ph)(SPh)₃(PEt₃)₃] (2), via formal addition of a “Ni(0)” equivalent, coupled with a CS oxidative addition step, which simultaneously generates the Ni‐bound phenyl ligand and the μ₃‐sulfide ligand. Upon gentle heating, complex 2 converts into a mixture of [Ni₅(S)₂(SPh)₂(PEt₃)₅] (3) and [Ni₈(S)₅(PEt₃)₇] (4), via further addition of “Ni(0)” equivalents, in combination with a series of C–S oxidative addition and CC reductive elimination steps, which serve to convert thiophenolate ligands into sulfide ligands and biphenyl. The presence of 1–4 in the reaction mixture is confirmed by their independent syntheses and subsequent spectroscopic characterization. Overall, this work provides an unprecedented level of detail of the early stages of Ni nanocluster growth and highlights the fundamental reaction steps (i.e., metal atom addition, CS oxidative addition, and CC reductive elimination) that are required to grow an individual cluster.