Opportunities of Immobilized Homogeneous Metathesis Complexes as Prominent Heterogeneous Catalysts

Abstract

A plethora of strategies for immobilizing well‐defined metathesis catalysts on solid supports have been developed over the past decades. Whereas most reviews on classical heterogeneous metathesis catalyst designs mainly discuss covalent binding approaches, we here extended this topic with non‐covalent surface science methods, a research area that gained interest recently. Within this context, the main focus was set on the immobilization of ruthenium alkylidenes or so‐called Grubbs complexes, as these catalysts are known for their high activity, stability and commercial viability. Besides giving an overview of different immobilization strategies, the wide diversity of supported Grubbs catalysts also allows for discussing implications of attaching Grubbs catalysts that go beyond the traditional benefits of heterogeneous catalysis, such as easy catalyst separation. More specifically, this Review will summarize several unique opportunities of immobilized homogeneous catalysts in liquid‐phase metathesis transformations in terms of impact on activity, stability, and product selectivity, as to highlight the economic potential, but without ignoring possible shortcomings and limitations.

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.…”

SBA-15 as a Support for Effective Olefin Metathesis Catalysts

“…Recently, new types of zeolites (mesoporous, two-dimensional [29][30][31]) have been shown to be interesting supports for new metathesis heterogeneous catalysts (vide infra). Several review articles and book chapters have been devoted to this topic [16,17,[32][33][34][35][36] and therefore we have exclusively focused on catalysts with a SBA-15 support and on their state-of-the-art features.…”

“…The confinement of catalysts in pores of different sizes Catalysts 2019, 9, 743 4 of 18 and shapes was also predicted to generate corresponding changes in catalyst selectivity. Therefore, various mesoporous sieves were used as supports to immobilize Schrock and Grubbs catalysts with varying degrees of success [16,17].…”

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.…”