Heterogenous Alkene Metathesis Species Identified

Methylidene and metallacyclobutane species of a heterogeneous catalyst have been identified as key intermediates in alkene metathesis, an important reaction for the industrial production of chemicals and polymers (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0802147105). Identifying reaction intermediates and determining their fate are critical steps toward understanding catalyst deactivation and improving catalyst performance. Christophe Copéret of the University of Lyon, in France, led a team that used solid-state NMR spectroscopy to monitor a tungsten alkylidene catalyst supported on silica during the metathesis reaction of ethylene and 2-butene to yield propylene. The intermediates the team observed for the heterogeneous catalyst are the same as those previously observed for homogeneous systems. The results add to evidence that supported catalysts behave similarly to their homogenous homologues. The additional insight into the reaction mechanism should, in turn, enable the design of more efficient catalytic systems, the authors say.