Reaction of heterometallic cubane-type cluster complexes—[Mo 3{Pd(dba)}S 4Cl 3(dbbpy) 3]PF 6, [Mo 3{Pd(tu)}S 4Cl 3(dbbpy) 3]Cl and [Mo 3{Pd(dba)}S 4(acac) 3(py) 3]PF 6, where dba—dibenzylideneacetone, dbbpy—4,4′-di- tert-butyl-2,2′-bipyridine, tu—thiourea, acac—acetylacetonate, py—pyridine, with white phosphorus (P 4) in the presence of water leads to the formation of phosphorous acid H 3PO 3 as the major product. The crucial role of the Pd atom in the cluster core {Mo 3PdS 4} has been established in the hydrolytic activation of P 4 molecule. The main intermediate of the process, the cluster complex [Mo 3{PdP(OH) 3}S 4Cl 3(dbbpy) 3] + with coordinated P(OH) 3 molecule and phosphine PH 3, have been detected by 31P NMR spectroscopy in the reaction mixture.