Oxides of the group VIb metals (Cr, Mo, W) and oxides of vanadium, rhenium, and niobium supported on a second high-surface-area metal oxide such as Al2O3, TiO2, Si02, ZrO2, and so forth are recognized as industrially important catalysts or catalyst precursors for various reactions [1–11], These materials frequently have been described as so-called monolayer catalysts based on a structural model which assumed spreading of the active oxide over the support surface. These catalysts have been investigated by a variety of techniques, conventional bulk sampling techniques as well as by surface-sensitive electron and ion spectroscopies, in an attempt to elucidate the nature of the catalyst surface species, and to study the coordination environment of the active metal center(s). Electronic spectroscopy gives rise to broad bands and the spectra are less informative than vibrational spectra. In addition, although techniques such as Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS...

Raman spectroscopy of monolayer-type oxide catalysts: Supported Mo oxides

Transition metal oxo complexes

Effect of calcination temperatures on microstructures and photocatalytic activity of tungsten trioxide hollow microspheres

Vibrational spectra of transition metal chalcogen compounds

https://core.ac.uk/download/pdf/15565323.pdf

Synthesis and characterization of tungsten trioxide powders prepared from tungstic acids

The infrared and mass spectra of MoO2Cl2, MoO2Br2, WO2Cl2, and WO2Br2 in the gas phase have been studied. The vapours contain mostly monomeric molecules but there is also a small amount of relatively unstable dimeric species present in each case. In inert solvents MoO2Cl2 and MoO2Br2 are dimeric and the infrared spectra are reported. In the solid state all four compounds are polymeric and the absence of the characteristic M = O infrared frequency suggests that only bridging oxygen atoms can be present. X-ray powder diffraction data suggest that the four compounds are isomorphous.

CG Barraclough

Papers

Spectral and structural studies of some Group VIA dioxydihalides