An alkene-bridged thioether ligand (L) was designed and used for its first study within a polyoxometalate (POM) hybrid system, and a POM-based copper(I)-alkene compound [(CuIL)2(PVMoVI12O40)]·(CuIL) (1) was isolated and characterized by X-ray crystallography. A unique alkene-coordinating N(η2-C═C)N mode of L is observed, and the Cu centers are captured by σ2,π-L in a pocket fashion, giving birth to discrete [CuIL]+ cations and [(CuIL)2(PVMoVI12)]- anions. The ionic crystal exhibits solubility in aprotic polar solvents, and the electrospray ionization mass spectrometry is used to explore the nature of species present in the solution. It is found that the whole cluster [PVMoVI12]3- is completely present, and all the main peaks can be assigned to different charged fragments of the same parent cluster.