Metathesis

Abstract

In organic synthesis and polymer science, the metathesis reaction consists of a unique metal‐catalyzed carbon skeleton redistribution in which a mutual exchange of unsaturated carbon–carbon bonds takes place. The reaction is generally reversible and limited to an equilibrium. In its most common embodiment, alkenes serve as reagents. Hence, olefin metathesis constitutes a powerful catalytic method for both cleaving and forming CC double bonds. Alkyne metathesis and ene–yne metathesis are also important synthetic pathways. All three types of metathesis occur intra‐ or intermolecularly and numerous combinations thereof are possible (ring‐closing metathesis, ring‐opening metathesis polymerization, cross‐metathesis, etc). Metathesis has opened up new routes to important petrochemicals, oleochemicals, polymers, and specialty chemicals. The transformation often gives access with remarkable atom economy to structures that are not available by any other means, or only via multistep painstaking procedures. Major industrial processes rely on metathesis for the production of olefins. They are usually based on inexpensive, ill‐defined, multicomponent catalytic systems derived from tungsten, molybdenum, rhenium, or ruthenium salts. Research laboratory applications take advantage of well‐defined metal‐alkylidene complexes of molybdenum and ruthenium that combine high activities and ease of set‐up under reproducible conditions, albeit at the price of a higher cost.

Formate‐Bicarbonate Cycle as a Vehicle for Hydrogen and Energy Storage

“…The nature and some activities of Ru are similar to the other members of 4d transition metal triad (i. e. Rh and Pd). Initially Ru catalysts were used in alkene metathesis reactions, however later on they were explored for the other reactions including dehydrogenation reactions [54] . Larson and co‐workers in 1979 proposed initial findings on Ru‐catalyzed formic acid decomposition followed by Sun and co‐workers in 1990 [55] .…”

Effect of resin staging on frontal polymerization of dicyclopentadiene

“…19 Using a latent catalyst system comprised of second-generation Grubbs catalyst inhibited by alkyl phosphites allows for controlling the pot life of DCPD resin up to 30 h. 20 The resulting polymer is polydicyclopentadiene, which is a high-performance thermoset with mechanical properties comparable to those of aerospace-grade epoxies. [21][22][23] It has also been found that the low reaction rates of the FP-DCPD resin at room temperature causes the resin to gradually transform from a low viscosity liquid to a frontally polymerizable viscoelastic gel. This rheological transformation of resin, while being frontally polymerizable, enables new applications from composite and nanocomposite manufacturing to freeform 3D printing to moldless fabrication of thermosetting objects.…”

Optical monitoring of polymerizations in droplets with high temporal dynamic range

“…Ring-opening metathesis polymerization (ROMP) catalysed by the ruthenium-based Grubbs Generation II (GG2) catalyst 76,77 was selected for the development of this monitoring strategy as it is relatively air and moisture-tolerant, easy to control, relatively well understood, and industrially relevant. 78,79 ROMP polymers and their derivatives are widely represented in both industrial catalysis and the development of specialized materials. 80 Diverse polymer morphologies and polyfunctional materials are now accessible via ROMP through reproducible means and under mild conditions.…”

“… 81 Many thousands of tons of polynorbornene polymers are produced industrially each year. 78 Specifically, the ROMP of norbornene to form polynorbornene was chosen as the primary reaction under study to explore this readout method.…”