Olefin Metathesis by Group VI (Mo, W) Metal Compounds

Abstract

Olefin metathesis is an important reactino not only in petroleum chemistry but also in fine chemistry. Professors Grubbs, Schrock, and Charin obtained the Nobel Prize in 2005 for the development of this reaction (determination of the mechanism and synthesis of homogeneous catalysts). This reaction can be described as the redistribution of carbon chains of olefins via a breaking of their C=C double bonds. It is catalyzed by metal carbenes and the catalytic cyclce passes through a metallacyclobutane. The purpose of this chapter is to give an overview of catalystss based on tungsten or molybdenum active for this reaction. Numerous tungsten and molybdenum organometallic complexes displaying a carbene functionality were synthesized. Some of them are highly active in olfein metathesis. INdustrially, tungsten oxide on silica is used as a precursor of the propene prodcution by olefin metathesis of but-2-ene and ethylene. However, the active sites are not well known but they can be modeled by grafting, via surface organometallic chemistry, perhydrocarby complexes of molybdenum or tungsten on oxide surfaces. After a review of the complexes used in homogeneous catalysis, a review of the industrial catalysts and their models will be given.