Reaction of in situ generated copper-monosubstituted Keggin polyoxometalate (POM) and copper-phenanthroline complexes in potassium or sodium acetate buffers led to the formation of the potassium salt of [[SiW(11)O(39)Cu(H(2)O)][Cu(2)(phen)(2)(H(2)O)(ac)(2)]](4-) (1) and [[Si(2)W(22)Cu(2)O(78)(H(2)O)][u(2)(phen)(2)(H(2)O)(ac)(2)](2)](8-) (2, where phen = phenanthroline and ac = acetate) hybrid polyanions, respectively. Both compounds are the first discrete mono- and bimolecular transition-metal-substituted Keggin POMs that support a binuclear copper-acetate complex. Despite the different nature of the POMs, the crystal packing of the two compounds is closely related, being formed of hybrid parallel layers that give rise to an alternate sequence of inorganic and metalorganic regions. This packing type seems to be determined by the extensive network of weak intermolecular interactions established by the dicopper complexes, as a Hirshfeld surface analysis shows. Electron paramagnetic resonance studies indicate that both the supported [Cu(2)(ac)(2)(phen)(2)(H(2)O)](2+) complexes and the copper(II)-monosubstituted POMs are magnetically isolated.