A New Ruthenium-Based Olefin Metathesis Catalyst Coordinated with 1,3-Dimesityl-1,4,5,6-tetrahydropyrimidin-2-ylidene: Synthesis, X-ray Structure, and Reactivity

The new ruthenium olefin metathesis catalyst 4 bearing a 5,5'-dimethyl-1,3-dimesityl-1,4,5,6-tetrahydropyrimidin-2-ylidene ligand was first synthesized from (PCy_3)_2(Cl)_2Ru ═ CHPh (1). The X-ray crystal structure of complex 4 has been determined and shows that the N-mesityl group of the six-membered carbene ligand and the benzylidene moiety are in close proximity (2.9 Å). This catalyst demonstrates moderate reactivity for both ring-closing olefin metathesis and ring-opening metathesis polymerization.