Here, we demonstrate this effect and show how visible light irradiation can be used to selectively target the partial reduction and metal-functionalization of {V12}, leading to a dimagnesium functionalized species, {Mg2V12}, as an intriguing model for future studies, e.g., in electrochemical energy storage. Starting point was our study into the design of magnesium(II)-functionalized {V12} as molecular models for Mg ion batteries, where solid-state magnesium vanadates are under investigation as active electrode materials. Initial experiments to functionalized {V12} with Mg 2+ were performed by reacting Mg 2+ with (DMA)2{V12} in acetonitrile under the standard placeholder-functionalization conditions described above. Despite extended variation of the reaction and isolation conditions, reproducible formation of Mg-functionalized {V12} was not possible. Systematic analysis of the key reaction parameters showed that visible light irradiation and oxygen-free conditions were required to access the target compound, (nBu4N)4[(MgCl)2V12O32Cl] (={Mg2V12}, 1). Diffusion crystallization using diethyl ether as diffusion solvent gave green single crystals of {Mg2V12} in yields of 64 % (based on {V12}). When the reaction was performed in the dark under otherwise identical conditions, only the starting material {V12} was recovered as yellow crystals.