Alternating ring-opening metathesis polymerization by Grubbs-type catalysts with N-pentiptycenyl, N-alkyl-NHC ligands

Abstract

A Grubbs-Hoveyda type catalyst with a N-pentiptycenyl, N-cyclohexyl-NHC ligand provides poly(nbe-alt-coe) with an excellent degree of alternation while lacking significant activity in the homopolymerization of cyclooctene.

In a Quest for Selectivity Paired with Activity: A Ruthenium Olefin Metathesis Catalyst Bearing an Unsymmetrical Phenanthrene‐Based N‐Heterocyclic Carbene

“…in an investigation of backbone steric hinderence influence on the reactivity of ruthenium alkylidene complexes (Figure , L13‐A , C ) . N ‐Cyclohexyl derivative was succesfully used in alternating ring‐opening metathesis polymerisation (AROMP), similarly to that previously published by the Plenio group N ‐pentiptycenyl ruthenium complex …”

“…[42][43][44][45] N-Cyclohexyl derivative was succesfullyu sed in alternating ringopeningm etathesis polymerisation (AROMP), [46] similarly to that previously published by the Plenio group N-pentiptycenyl ruthenium complex. [47] In line with the trend of investigating uNHC as ligandsf or olefin metathesis, our group published as eries of works on Naralkyl-N'-aryl NHC-based complexes.T hese provedu seful as olefin-metathesis precatalysts, not only,i ns tandard conditions under an argon atmosphere, but also in commercial grade nondegassed solvents (Figure 1, L10-B). [48,49] Importantly,t hose complexes were successfully applied in thee thenolysis of ethyl oleate (Figure 1, L12-B,C) [50] and afforded low isomerization in self-metathesis of a-olefins ( Figure 1, L11-C).…”

Ruthenium‐Catalyzed Alternating Ring‐Opening Metathesis Copolymerization of Norborn‐2‐ene with Cyclic Olefins

“…[1,2] However, the synthesis of precision polymers [1b] derived from the alternating copolymerization of two different monomers via ROMP, promoted by ruthenium-based catalysts, is still limited. [3][4][5][6][7][8][9] Only a few examples of alternating ROMP copolymers obtained using properly designed catalysts have been reported. [4][5][6][7] Chen and coworkers developed first generation ruthenium catalysts with modified, unsymmetrical steric environment around the metal center by introducing chelating phosphine/phenolate ligands.…”

“…[3][4][5][6][7][8][9] Only a few examples of alternating ROMP copolymers obtained using properly designed catalysts have been reported. [4][5][6][7] Chen and coworkers developed first generation ruthenium catalysts with modified, unsymmetrical steric environment around the metal center by introducing chelating phosphine/phenolate ligands. [4] These mechanistically designed systems were able to promote the copolymerization of NBE and COE with a high content of alternating NBE-COE diads.…”

“…[5a,b] Lately, Plenio and coworkers have presented a new class of Hoveyda-Grubbs type complexes, decorated with unsymmetrical N-alkyl, N'-pentiptycenyl NHC ligands (Figure 1), which are suitable for the highly selective synthesis of alternating NBE-COE copolymers. [7] The observed selectivity seems to be dominated by the high steric encumbrance offered by the pentiptycenyl group which causes the formation of reactive pockets, around the metal, of very different shape and size. Notably, the catalyst with an Ncyclohexyl, N'-pentiptycenyl NHC was found to give up to 98% of alternating diads at low NBE/COE ratio (1:10).…”