Olefin Metathesis-Active Ruthenium Complexes Bearing a Nucleophilic Carbene Ligand

Abstract

The reaction of [Cp*RuCl] 4 ( 1; Cp* = η 5 -C 5 Me 5 ) with the carbene ligand 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) affords a coordinatively unsaturated Cp*Ru(IMes)Cl ( 3 ) complex in 86% isolated yield. Solution calorimetric results in this system provide information concerning the electron donor properties of the carbene ligand, which are very similar to those of PCy 3 . Structural information from single-crystal X-ray studies for complex 3 allows the determination of steric parameters associated with this ligand. The thermochemical information is used to predict the magnitude of the enthalpic driving force behind substitution reactions involving RuCl 2 ( C(H)Ph)(PCy 3 ) 2 ( 1 ) and the carbene ligand, IMes, affording the RuCl 2 ( C(H)Ph)(PCy 3 )(IMes) ( 6 ) complex in high yield. A similar mixed carbene/phosphine ruthenium complex, RuCl 2 ( C(H)Ph)(PPh 3 )(IMes), can also be isolated from RuCl 2 ( C(H)Ph)(PPh 3 ) 2 and the IMes ligand. A single-crystal X-ray diffraction study has been performed on 6 . The thermal stability of these mixed phosphine/carbene ruthenium carbene complexes has been studied at 60 °C in toluene. Their catalytic activity has been evaluated for the ring closing metathesis of diethyldiallylmalonate.