BONDING OF ORGANOMETALLIC FRAGMENTS TO POLYOXOMETALATES

The chemistry of polyoxometallates has become a subject of great interest, since these compounds have been considered suitable models for understanding heterogeneous catalytic processes, while being very similar to organometallic complexes more widely known for their role in homogeneous processes. In order to develop a reliable model for the study of the interaction between polyoxometallates and organometallic fragments, a theoretical study based on extended Huckel calculations was done on the simple M6Ox derivatives, for which many experimental data are available. The charges, the relative energies of possible isomers, and the nature of the frontier orbitals are consistent with the known behavior of the organometallic adducts on which the model was based. A different isomerization pathway between the three isomers of cis-Nb2M4O19(RhCp)2- is suggested, based on the migration of the organometallic fragment over the surface of the polyoxometallate.