Linker‐Free, Silica‐Bound Olefin‐Metathesis Catalysts: Applications in Heterogeneous Catalysis

Abstract

A set of heterogenized olefin-metathesis catalysts, which consisted of Ru complexes with the H(2)ITap ligand (1,3-bis(2',6'-dimethyl-4'dimethyl aminophenyl)-4,5-dihydroimidazol-2-ylidene) that had been adsorbed onto a silica support, has been prepared. These complexes showed strong binding to the solid support without the need for tethering groups on the complex or functionalized silica. The catalysts were tested in the ring-opening-ring-closing-metathesis (RO-RCM) of cyclooctene (COE) and the self-metathesis of methyl oleate under continuous-flow conditions. The best complexes showed a TON>4000, which surpasses the previously reported materials that were either based on the Grubbs-Hoveyda II complex on silica or on the classical heterogeneous Re(2)O(7)/B(2)O(3) catalyst.

Nonaqueous and Aqueous Emulsion ROMP Reactions Induced by Environment-Friendly Latent Ruthenium Indenylidene Catalyst Bearing Morpholine Substituted Bidentate (N, O) Schiff Bases

“…In order to increase the scope of the study, Ru‐1 was supported on silica gel before RCM reaction. In a recent study that was reported by Limbach and co‐workers a set of ruthenium catalysts were adsorbed on silica gel and used as heterogeneous catalysts in several olefin metathesis reactions . We tried to adapt the same strategy to our catalyst system.…”

Heterogeneous olefin‐metathesis: Comparative perspective of the activity with respect to unsaturated fatty acid methyl esters

“…The stability and the strength of catalyst‐support interaction can be optimized by introducing a more compatible ligand in the organometallic complex, as has been demonstrated by Cabrera et al who tested H 2 ITap‐modified Hoveyda‐Grubbs type catalyst . The H 2 ITap, 1,3‐bis(2′,6′‐dimethyl‐4′dimethyl aminophenyl)‐4,5‐dihydroimidazol‐2‐ylidene, ligand acted as a resilient tethering group by getting protonated from the silanol groups of the support material and thus coordinating with the unmodified commercial silica material, most probably as a result of ionic interactions.…”

“…Hoveyda‐Grubbs type complexes: (a) SIMes‐modified Hoveyda‐Grubbs II complex; (b) H 2 ITap‐modified Hoveyda‐Grubbs II complex (reproduced with permission) …”

“…Self‐metathesis of methyl oleate under same reaction conditions − catalyst deactivation profile: HGII‐Figure a/SiO 2 –red line; HGII‐modified‐Figure b/SiO 2 –blue line (reproduced with permission) …”

Depolymerization of 1,4-polybutadiene by metathesis: high yield of large macrocyclic oligo(butadiene)s by ligand selectivity control

“…[16][17][18][19][20][21][22][23] Other methodologies such as ring-expansion metathesis polymerization of cycloolefins with cyclic Ru catalysts have also been explored. [24][25][26][27] The particular synthesis of macrocycles from 1,4-PB is only scarcely described, mainly in the context of PB degradation.…”