The difference in reactivity between 2 and 4 highlights the crucial role of the Mg centre flanking the Ge centre, despite it not being directly involved in bond breaking or electron transfer events. We argue that the Mg centre electronically stabilises the four-electron reduced ligand sufficiently to allow for this reactive state to be accessed. This provides a compelling 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.