The reaction of germylone (L)Ge (1) [L = 3-Ad-1-{C(tBu) = N(Mes)}C3H4N2] with 1 equivalent of MeOTf afforded a germyliumylidene ion [(L)GeMe]+OTf- (2), while reactions with M(CO)5(thf) (M = Cr, Mo, W) gave the corresponding germylone-metal complexes [(L)Ge]M(CO)5 (3-5). The former possesses a pyramidal Ge center, whereas the latter display a planar geometry around the Ge atom. Computational studies showed a unique bonding interaction between 1 and the M(CO)5 unit, which involves a σ-donation as well as a weak π-back-donation. © The Royal Society of Chemistry 2016.