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)2and 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-vertexnido-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.