On the isomerization of a trans-dichloro to a cis-dichloro amide-chelated ruthenium benzylidene complex and the catalytic scope of these species in olefin metathesis

Abstract

Upon comparative NMR spectroscopy studies, the isomerization of newly disclosed dichloro [κ2(C,O)-2-(N-propylaminocarbonyl)benzylidene][1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene]ruthenium from trans-dichloro configuration (SPY-5-31) to its thermodynamically more favored cis-dichloro derivative (with SPY-5-34 stereochemistry) was found to proceed via dissociation of one chloride ligand to form an intermediate cationic species. Furthermore, the performance of the trans- and the cis-dichloro derivatives as catalysts in ring-closing metathesis and as initiators in ring-opening metathesis polymerization was studied.