In conclusion, we report the isolation, synthesis, and characterisation of NHGe 2, featuring a vacant, redox-active binding pocket that is able to bind metals in close proximity to the Ge centre. This was demonstrated by the isolation of Ge-Zn (3) and Ge-Mg (4) complexes, with the versatile redox-active binding pocket accessing different oxidation states. We envision that complex 4 presents a promising entry point into germylene-(transition) metal chemistry, through transmetalation of the Mg centre in the bis-anionic binding site with various metal precursors. Electronic structure calculations reveal that the extent of the Ge-M dative interactions can vary as a function of the required electron density on the metal centre that occupies the redox-active binding pocket, with the Ge-Zn interaction in 3 being weak, whilst strong dative Ge-Mg interactions are found for 4. The latter engages in 'Metallo-Diels-Alder' reactions with a multitude of substrates containing C-C unsaturated bonds, activating the C-C bond over Ge and the ligand backbone. The same reaction does not proceed prior to two-electron reduction of the vacant binding site by Mg 0 . This provides a well-defined example of indirect cooperativity, where the Mg centre electronically stabilises the quadruply reduced ligand, upon which the germylene engages in metal-ligand cooperative activation of C-C unsaturated bonds. Combined, these findings not only expand the understanding of germylene reactivity but also open new avenues for designing systems that leverage cooperative interactions between germylenes and proximal metals for chemical transformations.