We have used discrete polyoxopalladates(II) (POPs) of the MPd12X8 nanocube- and Pd15X10 nanostar-types (M = central metal ion, X = capping group) as molecular precursors (diameter ca. 1 nm) for the formation of supported (SBA-15) metallic nanoparticles. These materials proved to be highly active in the hydrogenation of o-xylene. The characterization of such hydrogenation catalysts revealed that the average size of the resulting alloy particles is quite uniform with diameters ranging from 1 to 3 nm (indicating little to no agglomeration). The central transition-metal ion Mn+ (MnII, FeIII, CoII, NiII, CuII, ZnII, PdII) in the POP structure and also the nature of the capping group (AsO43–, SeO32–, PO43–, phenyl-AsO32–) influence the resulting catalytic performance.