Cluster expansion and vertex substitution pathways in nickel germanide Zintl clusters

Abstract

We describe the reactivity of the hypersilyl-functionalized Zintl cluster salt K[Ge₉(Hyp)₃] towards the nickel reagents Ni(COD)₂ and Ni(Cp)₂, which gives rise to markedly different complexes. In the case of Ni(COD)₂ (COD = 1,5-cyclooctadiene), a dianionic sandwich-like cluster [Ni{Ge₉(Hyp)₃}₂]²⁻ (1) was obtained, in line with a simple ligand substitution reaction of COD by [Ge₉(Hyp)₃]⁻. By contrast, when an analogous reaction with Ni(Cp)₂ (Cp = cyclopentadienyl) was performed, vertex substitution of the [Ge₉(Hyp)₃]⁻ precursor was observed, giving rise to the nine-vertex nido-cluster (Cp)Ni[Ge₈(Hyp)₃] (2). This is the first instance of vertex substitution at a hypersilyl-functionalized Zintl cluster cage. The electrochemical behavior of these compounds was explored and showed reversible redox behaviour for both clusters.