Modeling of Ru and Fe based olefin metathesis Michael T. FeldmannRichard P. MullerWilliam A. Goddard, IIIMaterials and Process Simulation Center, Caltech
Olefin metathesis is an important reaction for many chemical processes including polymerization. It has been shown that the Grubbs ruthenium-based catalyst is very efficient at olefin metathesis with high functional group tolerance. It has been so successful that we would quickly deplete the world of its supply of ruthenium if we were to use it for all its applications. Looking at related elements that have a higher natural abundance leads to iron. Iron should have similar electronic behavior which could lead to a successful iron based olefin metathesis catalyst.
The mechanism of the ruthenium-based Grubbs catalyst of the formula L2X2Ru=CHR has been examined. Experimentally it has been shown that L=PCy3,PiPr3, X=Cl, and R=CHPh2 produce an effective catalyst. When X=Cl and R=H in our theoretical study, L was varied from a simple phosphine to a carbene and an sp2 nitrogen donating ligand. Understanding gained from this mechanism has allowed for possible performance enhancement of the ruthenium-based catalyst. In addition, the iron-based analog is showing promise as the ligand effects are being understood and tuned to the needs of the iron-based reaction pathway.