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.