RAMAN STUDIES ON THE FORMATION OF 12-MOLYBDOPYROPHOSPHATE

The formation of a yellow 12-molybdopyrophosphate complex was ascertai ned in both solid and solution states. A Raman spectroscopic study rev ealed the spontaneous transformation of the parent 18-molybdopyrophosp hate anion, [(P2O7)Mo18O54](4-), via the 15-molybdopyrophosphate anion , [H-6(P2O7)Mo15O48](4-), into the 12-molybdopyrophosphate anion, [H-1 2(P2O7)Mo12O42](4-) in the CH3CN-water system. In contrast, 12-molybdo pyrophosphate was the only heteropoly species formed in aqueous soluti on. It turned out that the spectrophotometric determination of pyropho sphate with the Fiske-Subbarow reagent and the Rucena-Conde and Prat r eagent was based on the formation of the mixed-valence blue species of 12-molybdopyrophosphate.