Highly Active Metathesis Catalysts Generated In Situ from Inexpensive and Air-Stable Precursors

Abstract

The preparation of well‐defined ruthenium alkylidene complexes bearing N‐heterocyclic carbene ligands such as 1,3‐dimesitylimidazol‐2‐ylidene (1) and 4,5‐dihydroimidazol‐2‐ylidene (2) have led to catalysts (such as 3 and 4; see Figure 1) which are highly active in ring‐closing metathesis (RCM), cross metathesis (CM), and ring‐opening metathesis polymerization (ROMP).1 These catalysts show increased thermal stability and similar tolerance to oxygen and moisture when compared to their parent bisphosphane complexes, [(PCy_3)_2Cl_2Ru=CHPh] (5, Figure 1).2 Since all synthetic routes to catalysts 3 and 4 proceed through the transformation of a ruthenium bisphosphane carbene,3 a direct route through readily available starting materials is still desirable.