Cluster expansion and vertex substitution pathways in nickel germanide Zintl clusters

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 compounds. In the case of Ni(COD)2, a dianionic sandwich-like compound [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 nickelocene 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.