Highly Active Catalysts in Alkene Metathesis: First Observed Transformation of Allenylidene into Indenylidene via Alkenylcarbyne—Ruthenium Species

Abstract

A cat. for all seasons: The transformation of the allenylidene‐ruthenium complexes [RuCl(η6‐arene)(CCCR2)(PR${{{\prime \hfill \atop 3\hfill}}}$)][CF3SO3] into indenylidene species [RuCl(η6‐arene)(indenylidene)(PR${{{\prime \hfill \atop 3\hfill}}}$)][CF3SO3]2 by the simple protonation with CF3SO3H and formation of an alkenylcarbyne intermediate (see picture; arene=p‐cymene) is observed by low temperature NMR experiments. The new in situ generated 18 electron ionic indenylidene species are highly active in the polymerization of cyclooctene and cyclopentene, ring‐closing metathesis of dienes and enynes, and the acyclic diene metathesis of decadiene, thus making it a catalyst for all seasons.

Chelating η6‐Arene‐η1‐carbene Ligands in Ruthenium Complexes

“…J. Indeed, the [Ru=C=C=CPh 2 (Cl)(PCy 3 )(p-cymene)]X [13] complexes were shown to be active precursors for ROMP on either thermal [14] or acid-promoted [15] transformations into indenylidene-ruthenium derivatives. The indenylidene carbene plays the role of alkene metathesis initiator in these catalyst precursors.…”

Early Steps of Homogeneous Catalysis in Rennes: Carbon Dioxide Incorporation, Alkyne Activation and Ruthenium Catalysis

“…First the search for evidence of active vinylidene-ruthenium species in the ruthenium(II) activation of terminal alkynes has been the first step to develop the topic of carbon-rich ruthenium systems with D. Touchard [93] and A. Romero, via the characterization of vinylidene-allenylidene-and cumulenylidene-ruthenium complexes [94][95][96]. Among these we reported in 1998 the evidence for the first allenylidene-ruthenium catalytic precursors for alkene metathesis [72,97], and R. Castarlenas demonstrated that the resulting catalytic species was the corresponding indenylidene-ruthenium complex easily generated on protonation of the allenylidene-ruthenium parents [98,99]. Indenylidene-ruthenium catalysts are now commonly used in catalysis based on their efficiency and the easiness of preparation from simple propargylic alcohols rather than from diazoalkanes [72,73].…”

Recent developments in design and synthesis of well-defined ruthenium metathesis catalysts – a highly successful opening for intricate organic synthesis

“…51 For example, in Similarly, when using the same catalytic system, 99% pyrroline N-tosylamide was produced in RCM of diallyl tosylamide, after 10 minutes reaction time (Scheme 28) whereas in enyne metathesis of allylpropargyl tosylamide 75% of 3-vinylpyrroline N-tosylamide was obtained, under the same conditions. It is important to point out that in ring-opening metathesis polymerization (ROMP) of cyclooctene with the system [RuCl(p-cymene)(=C=C=CPh 2 )(PCy 3 )][CF 3 SO 3 ]/ HOSO 2 CF 3 , in chlorobenzene, an unexpectedly high yield of polyoctenamer was obtained after a short reaction time at room temperature (Scheme 30), whereas when starting from a less reactive monomer, cyclopentene, a maximum yield of 67% could be reached even after 1 hour at 0°C.…”