Synthesis and Catalytic Properties of Sulfur-Chelated Ruthenium Benzylidenes Bearing a Cyclic (Alkyl)(amino)carbene Ligand

Sulfur-chelated
ruthenium olefin metathesis precatalysts that possess
cyclic (alkyl)­(amino)­carbenes (CAAC) can benefit from the synergetic
effect of both ligands. Changing the steric bulk of the CAAC ligand
by using different substitution patterns was shown to affect the geometry
of the complexes produced and determined whether the complexes could
be catalytically dormant. The cis-dichloro latent
catalysts could be activated both by heat or light, even in the visible
region, for representative acyclic diene metathesis and ring-opening
metathesis polymerization reactions, olefin cross-metathesis, and
ring-closing metathesis without isomerization byproducts. Thus, these
complexes were shown to combine the uniqueness of CAAC-containing
Ru olefin metathesis catalysts with the advantage of the thermal and
photolatency imposed by sulfur chelation of the benzylidene.