SIMes/PCy3 mixed ligand‐coordinated alkyl group‐tagged ruthenium indenylidene complexes: Synthesis, characterization and metathesis activity

We report on the synthesis and characterization of SIMes/PCy3 mixed ligand‐coordinated second‐generation ruthenium catalysts, bearing various 3‐alkyl‐1‐indenylidene ligands, denoted as RuCl2(3‐alkyl‐1‐indenylidene)(SIMes)(PCy3), in which alkyl is isopropyl (4f), tert‐butyl (4g) or cyclohexyl (4h). The characterization of complexes 4f–4h was performed using infrared spectroscopy, elemental analysis, high‐resolution mass spectrometry and NMR spectroscopy. In addition, the configuration of complexes 4f and 4g was analyzed using single‐crystal X‐ray diffraction analysis. The catalytic activities of 4f–4h were evaluated in the olefin metathesis reaction of the ring‐closing metathesis of diethyl diallylmalonate, and the ring‐opening metathesis polymerization of cis,cis‐cyclooctadiene in comparison with the reference complex 4a. The results reveal that all complexes 4a and 4f–4h exhibit similar catalytic activity towards the tested substrates. Careful analysis of the catalyst performance and single‐crystal X‐ray diffraction data of the obtained complexes reveals that the steric modification on the 3‐alkyl group shows a negligible influence on the ligand congestion around the ruthenium center as well as on the catalytic activities in the metathesis reactions. The synthesis and characterization are reported of SIMes/PCy3 mixed ligand‐coordinated second‐generation ruthenium catalysts, bearing various 3‐alkyl‐1‐indenylidene ligands, denoted as RuCl2(3‐alkyl‐1‐indenylidene)(SIMes)(PCy3), in which alkyl is isopropyl, tert‐butyl or cyclohexyl. The catalytic activities of the complexes were evaluated in the olefin metathesis reaction.