Ruthenium Catalyst Metathesis

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Aspects of the latter topic were reviewed recently by Cavallo alkylidene.

This process has been studied heavily, particularly in recent years.

A wide range of pre-catalysts are known, the majority of which bear N-heterocyclic carbene (NHC) ligands, Metathesis pre-catalysts typically feature a so-called "throw-away" ligand which is not present in the active catalyst; this is typically a chelating alkoxystyrene group or a phosphine, although a wide range of such ligands have been employed.

Work continues in this field, to elucidate the finer mechanistic details.

The first detailed study of the initiation mechanism of this class of catalysts was carried out by Plenio, who studied the initiation of GH2 and Grela2 using UV/visible spectroscopy.

Kinetic experiments showed that the initiation rates of GH2 and Grela2 depended on the identity and concentration of the alkene substrate.Here, we consider the developments that are of most relevance to the ruthenium-catalysed homogeneous alkene metathesis reaction, for which a more detailed mechanistic outline can be found in Scheme 2.Key processes include: the study of pre-catalyst initiation, during which a stable pre-catalyst (typically 16e species; the study of how the ancillary ligand affects reactivity; the partitioning between intra- and inter-molecular metathesis pathways; the study and understanding of the key steps that occur during metathesis reactions, the development of -selective metathesis pre-catalysts; and the study of catalyst decomposition. Wiley Online Library requires cookies for authentication and use of other site features; therefore, cookies must be enabled to browse the site.Detailed information on how Wiley uses cookies can be found in our Privacy Policy.Naphthalene-based Hoveyda-type complexes have been explored in metathesis; studies of complexes 2–4 suggest that the degree of aromaticity is important in determining initiation rate.and so the catalyst is only active at high temperatures, but exhibits excellent stability under ambient conditions.While the fundamental series of [2 2]cycloadditions and retro[2 2]cycloadditions that make up the pathways of ruthenium-catalysed metathesis reactions is well-established, the exploration of mechanistic aspects of alkene metathesis continues.In this Feature Article, modern mechanistic studies of the alkene metathesis reaction, catalysed by well-defined ruthenium complexes, are discussed.Highly σ-donating phosphines were proposed to be best able to stabilise the MCB.Later work established that the first step in the mechanism was in fact phosphine dissociation (P NMR spectroscopy, to probe the rate of exchange of free phosphine with bound phosphine, and (ii) the reaction of the pre-catalysts with ethyl vinyl ether (EVE), for which phosphine dissociation was shown to be rate limiting (Scheme 4).


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