Rendering Schrock‐type Molybdenum Alkylidene Complexes Air Stable: User‐Friendly Precatalysts for Alkene Metathesis

Abstract

A matter of convenience: Schrock molybdenum alkylidenes are amongst the most powerful olefin metathesis catalysts known to date, but their sensitivity to air and moisture mandates their handling in a glove-box or by Schlenk techniques. This inconvenience is circumvented by using the corresponding phenanthroline- or bipyridine adducts, which are bench-stable and hence very user-friendly. The active species can be liberated from these precatalysts in uncompromised form on treatment with ZnCl₂ in toluene

5.27 Ene–Yne Metathesis

“…Recently, the Schrock catalysts have been rendered significantly more bench stable through complexation with 2,2 0 -bipyridine. 136 This practical advance will facilitate the use of these catalysts in synthetic laboratories. For RCEYM, the reactivity issue has been solved through tailored catalyst design.…”

Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes

“…vi Eighteen electron Mo(NAr)(CH 2 )[OC(CF 3 ) 2 Me] 2 (bipy) is inactive as a metathesis catalyst and stable toward bimolecular decomposition reactions. Fürstner has reported that bipyridine adducts of several related molybdenum species are relatively stable to air and can be activated toward metathesis in the absence of air in solution through addition of ZnCl 2 to remove bipyridine; viia apparently little exchange of alkoxide for chloride on the molybdenum is observed during the activation process. He also has reported examples of 18 electron alkylidyne complexes that are relatively stable in air and can be activated through addition of Lewis acids.…”

“…He also has reported examples of 18 electron alkylidyne complexes that are relatively stable in air and can be activated through addition of Lewis acids. viib Other types of 18 electron alkylidene complexes that are activated upon addition of Lewis acids are known. viii …”

A hexahydro-s-indacene based NHC ligand for olefin metathesis catalysts

“…Complexes 10 and 11 compare favorably with a few of the recently published catalyst complexes [19,35e38], but are on the other hand not significantly better than the most active catalysts [12,22,39,40]. Nonetheless it has to be conceded that the concept of this work (i.e.…”