Coordinating Additives as Activity Modulators in Diiodo Latent Olefin Metathesis Catalysts. Issue 4 (24th January 2023)

• Record Type: Journal Article
• Authors: Nechmad, Noy B.; Iudanov, Keren; Tarannam, Naziha; Kobernik, Victoria; Kozuch, Sebastian; Lemcoff, N. Gabriel
• Is Part Of: ChemCatChem. Volume 15:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-24
• Subjects: Coordinating additives -- Iodide ligands -- Ring-closing metathesis -- ROMP -- Ruthenium; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.202201690
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: The ruthenium alkylidene catalyzed ring‐closing metathesis (RCM) of 5‐membered rings is an intramolecular reaction that is highly favored due to entropic and enthalpic contributions. Counterintuitively, by using trifluoromethyl sulfur‐chelated ruthenium benzylidene (Ru−SCF3 −I ), RCM of a diene with a hindered dimethyl terminus, diethyl 2‐allyl‐2‐(3‐methylbut‐2‐en‐1‐yl) malonate (S1 ), could be achieved at high concentrations but not at low concentrations. This finding led to the discovery that several additives, including ethyl acetate, significantly enhance the latent catalyst's activity. DFT computations and NMR control experiments suggest that additive coordination influences the catalytic cycle. Moreover, the "ethyl acetate effect" was studied in ring‐opening metathesis polymerizations (ROMP), providing a more efficient initiation when the reactions are run in environmentally friendly ethyl acetate as the solvent. The strong influence of simple coordinating additives (sometimes present in the substrate itself) on the activation of latent catalysts provides important insights into the reaction mechanism and opens a doorway towards improving the efficiency of these types of catalysts. Abstract : Ru−SCF3 −I initiates ring‐closing metathesis of hindered substrates at high concentrations, while no reaction occurs at low substrate concentrations and low catalyst loadings. Adding ethyl acetate to the reaction mixture induces reactivity at ten times less catalyst loading. The additive coordinates to the metal center and activates the latent trans‐ diiodo catalyst.