Polyhedral main group element clusters of tetrel elements are discussed as suitable building units to form atom-precise nano-structures. Herein we report the oxidative coupling of two [Ge9{Si(TMS)3}2]2- clusters (TMS = trimethylsilyl) resulting in the dimeric cluster [Ge9{Si(TMS)3}2]22-. The dimer is structurally characterized as the [NHCiPrCu]+ adduct {NHCiPrCu[Ge9{Si(TMS)3}2]}2 [NHCiPr = 1,3-di(isopropyl)imidazolylidine]. The linkage of two molecular [Ge9{Si(TMS)3}2]2- anions under formation of an exo Ge-Ge bond occurs in the presence of Cy2BCl (Cy = cyclohexyl) and is mediated by trace amounts of oxygen as indicated by the isolation of the by-product Cy2B-O-BCy2.