A well-defined silica-supported tungsten oxo alkyl species displays high and sustained activity in propene metathesis, outpacing the parent imido derivative.

We report on the study of a set of rhenium oxide reference compounds (NH4ReO4, NaReO4, ReO3, ReO2, and Re2O7) using x-ray-absorption near-edge structure. The parallel use of Re L1 and L3 absorption edges permits a concomitant understanding of both the oxidation state and the local symmetry for these compounds. Experiments are compared with ab initio simulations. A good agreement is reached in most cases. The choice of the cluster size and the calculation method (full potential or not), which are mandatory ingredients allowing a satisfactory reproduction of the recorded spectra, is discussed in detail. In the meantime, these parameters give important pieces of information on the studied materials.