The commercially available catalyst cis-Caz-1 is extremely robust, especially when reactions are performed in an atmosphere of air. This phosphite-containing ruthenium complex only shows olefin metathesis activity at high temperatures. Herein, we report photoactivation of cis-Caz-1 at room temperature with UVA light. Thus, a wide variety of olefin metathesis reactions was performed under mild conditions with good yields. In addition, we report the synthesis, characterization, and catalytic activity of a phosphite-chelated ruthenium benzylidene complex, cis-PhosRu-1, which can be efficiently activated either by irradiation with visible light (λ = 405 nm) or by heat.

Several olefin metathesis reactions are studied, namely, jojoba oil oligomerization, methyl oleate self-metathesis, ring-closing metathesis (RCM) to form a nitrogen heterocycle, and 1,5-hexadiene acyclic diene metathesis polymerization (ADMET). The catalyst containing the Bertrand−Grubbs cyclic alkyl amino carbene (CAAC) ligand showed high selectivity by diminishing isomerization reactions; this was especially clear at high temperatures where the more widely used nitrogen heterocyclic carbene (NHC)-based catalysts show side reactions. Experimental and computational studies determined that it is much more difficult to produce ruthenium hydrides with CAAC, a property that can explain the improved observed activity. This finding opens a pathway for the development of even more selective olefin metathesis catalysts for reactions that require harsh conditions.

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.

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Efficient light-and thermal-activated metathesis reactions of tetra-substituted olefins were obtained by the Schelated ruthenium precatalyst Tol-SCF 3 . Its reactivity in a series of benchmark olefin metathesis reactions was compared to previously reported Mes-SCF 3 and a novel sterically congested S-chelated complex, Dipp-SCF 3 . Tol-SCF 3 is thus the first latent catalyst proven to be capable of promoting olefin metathesis of demanding substrates upon light stimulation at room temperature.