Ruthenium Olefin Metathesis Catalysts Bearing a Macrocyclic N‐Heterocyclic Carbene Ligand: Improved Stability and Activity. Issue 24 (13th April 2022)

• Record Type: Journal Article
• Authors: Kośnik, Wioletta; Lichosyt, Dawid; Śnieżek, Marcin; Janaszkiewicz, Angelika; Woźniak, Krzysztof; Malińska, Maura; Trzaskowski, Bartosz; Kajetanowicz, Anna; Grela, Karol
• Is Part Of: Angewandte Chemie international edition. Volume 61:Issue 24(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-13
• Subjects: Catalyst Design -- N-Heterocyclic Carbenes -- Olefin Metathesis -- Reaction Mechanisms -- Ruthenium; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202201472
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Formation of sterically hindered C−C double bonds via catalytic olefin metathesis is considered a very challenging task for Ru catalysts. This limitation led to the development of specialised catalysts bearing sterically reduced N‐heterocyclic carbene (NHC) ligands that are very active in such transformations, yet significantly less stable as compared to general purpose catalysts. To decrease the small‐size NHC catalysts susceptibility to decomposition, a new NHC ligand was designed, in which two sterically reduced aryl arms were tied together by a C‐8 alkyl chain. The installation of this macrocyclic ligand on the ruthenium centre led to the formation of an olefin metathesis catalyst ( trans ‐Ru6 ). Interestingly, this complex undergoes transformation into an isomer bearing two Cl ligands in the cis ‐arrangement ( cis ‐Ru6 ). These two isomeric complexes exhibit similarly high thermodynamic stability, yet different application profiles in catalysis. Abstract : New Grubbs‐type complexe containing macrocyclic N‐heterocyclic carbene ligand with two small aryl arms tied together was obtained and characterised. Interestingly, it can exist in two forms, cis and trans . Both of them exhibit similarly high thermodynamic stability, yet different application profiles in catalysis, however both can be used in difficult metathesis reactions, also leading to the formation of tetrasubstituted double bonds.