PEROXO-OXOMETALLATE FORMATION UNDER PHASE-TRANSFER CONDITIONS

The peroxidation of molybdenum(VI) and tungsten(VI) was investigated in the biphasic system water-chlorobenzene to elucidate the nature of the entities formed and transferred into the organic phase by phase transfer catalysts (PTC). It was observed that application of excess hydrogen peroxide to the acidic aqueous phase resulted in the exhaustive disaggregation of isopolyoxometallates, and the simple diperoxo-metallates were transferred by PTC. When the heteroatom (X, in the form of PO43-or AsO43-) was applied in a quantity commensurable with that of the metal ion (M), heteropolyoxometallates could be extracted in which the ratio M/X was determined by the concentrations of X and PTC. In the presence of excess hydrogen peroxide, peroxoheteropolyoxomolybdates with an Oact/M ratio of 2:1 were formed. Observations suggested that in the latter species the XO4 or X2O7 core is coordinated by diperoxo-oxometallate units. Through the use of different PTCs, several peroxoheteropolyoxometallates were isolated and investigated. © 1990.