Olefin Metathesis Catalyzed by a Latent Ruthenathiete Complex

Four-membered chelate complexes of ruthenium are rare, with only a handful of examples present in the literature. The first four-membered sulfur chelate, a cis-dichloro ruthenathiete complex, is reported to demonstrate latency toward olefin metathesis reactions until heated or irradiated with UV light. This complex's reactivity was benchmarked through ring-closing metathesis, cross-metathesis, and ring-opening metathesis polymerization reactions in deuterated chloroform and toluene as solvents. Despite the more strained 4-membered ring, the complex displays similar latency to 5-membered analogs previously reported in the literature. Key H-π interactions were observed between the mesityl methyl groups on the N-heterocyclic carbene and the aromatic groups on the alkylidene ligand, which are proposed to play a central role in the stability of the ruthenathiete. Collectively, this introduces a new class of sulfur-chelated ruthenium complexes for use in stimuli-promoted metathesis reactions.