Highly efficient nitrogen chelated ruthenium carbene metathesis catalysts†
A series of nitrogen chelated ruthenium carbene metathesis catalysts containing an N-heterocyclic carbene (NHC) and a carbonyl group have been developed and their catalytic activities for olefin metathesis reactions were investigated. The X-ray structure of the [(H2IMes)(Cl)2Ru]C(H)CH2[p-F(C6H3)NC(CF3)(C(O)OCH2CH3)] complex shows that the carbonyl oxygen of the ester and the imine nitrogen are both coordinated to the Ru metal to give an octahedral structure. The catalytic activity of these ruthenium carbene complexes for olefin metathesis reactions was tested. Some of the complexes bearing electron withdrawing groups had high initiation rates. These complexes exhibited excellent performance for both ring-closing metathesis and cross metathesis.