CATALYTIC-OXIDATION AND AMMOXIDATION OF PROPYLENE - MODELING STUDIES ON WELL-DEFINED MOLYBDENUM COMPLEXES

Molybdenum (VI)-allyloxo and -allylamido complexes possessing ancillary oxo and imido ligands have been synthesised and their subsequent decomposition studied in the perspective of modelling the postulated surface intermediates of the catalytic oxidation and ammoxidation of propylene. In solution and under mild conditions, these complexes undergo two types of reactions corresponding effectively to certain elemental steps of the heterogeneous processes, i.e. oxidative dehydrogenation of the allyl groups and allyl migration to oxo and imido functions. The mechanisms and the relative rates of these reactions are compared with that proposed for the surface catalytic chemistry. The possibility of alternate reaction pathways is discussed such as for C-N bond formation and the involvement of an allylideneamine intermediate in the catalytic cycle.