Differentiation of mono-oxo and polyoxo and of monomeric and polymeric vanadate, molybdate and tungstate species in metal oxide catalysts by IR and Raman spectroscopy

The expected and experimental features of vanadate, molybdate and tungstate species observed in inorganic compounds of different structures are discussed. In particular, fourfold coordinated species (truly tetrahedral and distorted tetrahedral), isolated and polymeric mono-oxo and dioxo metallyl species are discussed. On these bases, some of the data concerning surface species in oxide-supported oxides are also considered. The need to perform both IR and Raman experiments and, if possible, O-18/O-16 exchange experiments is also emphasized. Copyright (C) 2002 John Wiley Sons, Ltd.