[(μ2-H)(η2-Ge4)ZnPh2]3-, an edge-on protonated E4 cluster establishing the first three-center two-electron Ge-H-Ge bond.

The first example of a protonated and a rare example of a metal complex of the tetrahedral tetrel cluster anion [Ge4]4- was obtained from a solution of K6Rb6Ge17 in liquid ammonia in the presence of ZnPh2 and [18]crown-6. In [K([18]crown-6)][Rb([18]crown-6)]2[HGe4ZnPh2]·8NH3 (1) one ZnPh2 molecule and one H atom are bound to opposite, significantly elongated edges of a distorted Ge4 tetrahedron. DFT calculations confirm the experimentally found interatomic distances and reveal a structural proof of a three-center two-electron Ge-H-Ge bond.