Unprecedented Selectivity of Ruthenium Iodide Benzylidenes in Olefin Metathesis Reactions

Abstract

The development of selective olefin metathesis catalysts is crucial to achieving new synthetic pathways. Herein, we show that cis‐diiodo/sulfur‐chelated ruthenium benzylidenes do not react with strained cycloalkenes and internal olefins, but can effectively catalyze metathesis reactions of terminal dienes. Surprisingly, internal olefins may partake in olefin metathesis reactions once the ruthenium methylidene intermediate has been generated. This unexpected behavior allows the facile formation of strained cis‐cyclooctene by the RCM reaction of 1,9‐undecadiene. Moreover, cis‐1,4‐polybutadiene may be transformed into small cyclic molecules, including its smallest precursor, 1,5‐cyclooctadiene, by the use of this novel sequence. Norbornenes, including the reactive dicyclopentadiene (DCPD), remain unscathed even in the presence of terminal olefin substrates as they are too bulky to approach the diiodo ruthenium methylidene. The experimental results are accompanied by thorough DFT calculations.

Coordinating Additives as Activity Modulators in Diiodo Latent Olefin Metathesis Catalysts

“…Anionic ligands have shown a crucial influence on the efficiency and selectivity of the olefin metathesis reaction [6] . Given the remarkable ease by which anionic ligands may be replaced in complexes with cis‐ dihalo configurations, we have broadly studied this permutation for S‐chelated complexes; in particular, the effect of iodides as anionic ligands in Ru−SPh−I [7,8] and Ru−SCF 3 −I [9] (Figure 1). These special complexes displayed unique olefin metathesis reactivity and selectivity [10] .…”

Ruthenium Olefin Metathesis Catalysts with Six-Membered Chelating Dithioacetal Ligands: Synthesis and Reactivity

“…In the past few decades, our group and others have developed different Ru–X (X = S, S=O, P, Se, and N) chelated precatalysts for olefin metathesis reactions, especially for ring-opening metathesis polymerization (ROMP). − Introducing these chelating benzylidene ligands naturally decreased the initiation rates of the catalysts, given that dissociation of the chelated ligand is a necessary requirement to ignite the catalytic cycle. Notably, Ru–S chelation produced complexes with a cis -dichloro structure that rendered them inactive for most metathesis processes under ambient conditions (Figure ).…”

“…17,18,20 Further modifications, such as replacing the substituent on the chelating sulfur atom or exchanging the anionic ligands, also significantly altered the properties of the catalysts. 34,38,39,44,47,49 Most importantly, the use of light in novel metathesis applications, including the 3D printing of ROMP polymers, the guiding of chromatically orthogonal chemical reactions, or their integration with plasmonic Au nanoparticles, has significantly boosted the study of these latent catalysts. Despite the extensive studies and uses of Ru−S fivemembered chelated complexes, there are very few reports on Ru−S benzylidenes having six-membered chelation.…”

“…Notably, Ru–S chelation produced complexes with a cis -dichloro structure that rendered them inactive for most metathesis processes under ambient conditions (Figure ). These precatalysts could be activated by applying heat or light irradiation through a unique mechanism involving isomerization of the dormant cis -dichloro species into an active trans -dichloro configuration. ,, Further modifications, such as replacing the substituent on the chelating sulfur atom or exchanging the anionic ligands, also significantly altered the properties of the catalysts. ,,,,, Most importantly, the use of light in novel metathesis applications, including the 3D printing of ROMP polymers, the guiding of chromatically orthogonal chemical reactions, or their integration with plasmonic Au nanoparticles, has significantly boosted the study of these latent catalysts. ,− …”

The Impact of Water on Ru-Catalyzed Olefin Metathesis: Potent Deactivating Effects Even at Low Water Concentrations

“…Slow initiation 40 is again a plausible contributor, in addition to the bulk and poor H-bonding capacity of the iodide ligands. 29 , 34 , 35 …”