Ruthenium Carbenes Supported on Mesoporous Silicas as Highly Active and Selective Hybrid Catalysts for Olefin Metathesis Reactions under Continuous Flow

Abstract

In the search for a highly active and selective heterogenized metathesis catalyst, we systematically varied the pore geometry and size of various silica-based mesoporous (i.e., MCM-41, MCM-48, and SBA-15) and microporous (ZSM-5 and MWW) versus macroporous materials (D11-10 and Aerosil 200), besides other process parameters (temperature, dilution, and mean residence time). The activity and, especially, selectivity of such "linker-free" supports for ruthenium metathesis catalysts were evaluated in the cyclodimerization of cis-cyclooctene to form 1,9-cyclohexadecadiene, a valuable intermediate in the flavor and fragrance industry. The optimized material showed not only exceptionally high selectivity to the valuable product, but also turned out to be a truly heterogeneous catalyst with superior activity relative to the unsupported homogeneous complex.

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

“…[460][461][462] In contrast to d 0 systems,h omogeneous Ru metathesis catalysts have no corresponding heterogeneous industrial counterparts and will not be discussed here. However,s upported Ru-based catalysts have been prepared by SOMC, [463] SHC, [40,[464][465][466][467] and adsorption [468][469][470][471] techniques.…”

Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

“…Im Gegensatz zu d 0 ‐Systemen haben homogene Ru‐Metathesekatalysatoren keine heterogenen industriellen Entsprechungen und werden hier nicht weiter diskutiert. Trägerkatalysatoren auf Ru‐Basis sind mit SOMC‐, SHC‐ und Adsorptionsverfahren hergestellt worden.…”

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.…”