Orbital Interactions in the Ruthenium Olefin Metathesis Catalysts

Abstract

The structural and bonding interactions of the ruthenacyclobutane 4 suggested its nonclassical nature. A strong bonding interaction between the orbitals of the −CH2CH2CH2− fragment and the dy2 orbital on the metal in 4 was found that indicated the presence of two α-CC agostic interactions in the complex. Further, in the transition state corresponding to the rate-determining step of the metathesis, mutually benefiting π interactions exist between the RuCH2 and the olefin fragments. These features are important in the metathesis activity of Grubbs first-generation catalyst because they make the potential energy surface of the M(CH2)(C2H4) ↔ M(C2H4)(CH2) region flat.