Mechanism of olefin metathesis over a supported molybdenum catalyst

The metathesis of mixtures of 2,8-decadiene and 2,8-decadiene-1,1,1,10,10,10-d6 was carried out over a MoO2/CoO/Al2O3 catalyst. From the ratio of the product 2-butenes-d0:d3:d6, it was determined that the reaction proceeded by a chain mechanism, as described by the Chauvin scheme. During the initiation stages of the reaction propylene was formed and the reaction showed a significant isotope effect. This observation is best explained by the formation of a π-alkyl complex as a key intermediate in the initiation step.