Milder routes to chelated ruthenium complexes for Z-selective metathesis

A novel method to effect the salt metathesis and C-H activation of ruthenium-based, Z-selective metathesis catalysts contg. a chelated N-heterocyclic carbene (NHC) ligand using sodium carboxylates is reported. This method allows for the successful formation of stable chelated species contg. a variety of alterations to the NHC ligand that had decompd. under the previous approach. As such, several new, chelated metathesis-active ruthenium complexes are described, including a catalyst system exhibiting >95% Z-selectivity and record TONs (up to 8100) in homodimerization reactions of terminal olefins. Moreover, a catalyst has been synthesized that gives highly cis, highly tactic polymers via ring opening metathesis polymn. of strained, cyclic olefins, marking the first time tactic polymers have been made using a ruthenium-based metathesis catalysts.