Ruthenium–Indenylidene Complexes Bearing Saturated N-Heterocyclic Carbenes: Synthesis and Application in Ring-Closing Metathesis Reactions

摘要

The synthesis of complexes of the general formula Cl_2Ru(SIMes)(L)(3- phenylinden-l-ylidene), 3a (L = PCy_3), 3b (L = PPh_3), 3c (L = py) and Cl_2Ru(SIMe)(L)(3-phenylinden-l-ylidene), 4c (L = PCy_3), 4b (L = PPh_3), 4c (L = py) from commercially available Cl_2Ru(PR_3)_2(3-phenylinden-l-ylidene), 2a (R = Cy), 2b (R = Ph), is reported, and the summed complexes proved to be useful catalysts for various ring-closing metathesis reactions. The catalytic data reported furthermore demonstrate that the substitution pattern of the N-aryl group has a definite influence on the activity of the second generation indenylidene catalysts for a given metathesis reaction, i.e. catalysts containing the SIMe-ligand showed improved initiation compared to the more robust SIMes substituted catalysts. A strong temperature effect was observed on all of the reactions tested. It is shown that complexes containing the SIMe-ligand display higher initiation efficiency then their corresponding SIMes analogues.