Ruthenium indenylidene complex

Indenylidene-Ruthenium Complexes the Alkene Metathesis Catalytic Species from Allenylidene Ruthenium Complexes... 

Scheme 8.11 Formation of indenylidene ruthenium complex accelerated bythe protonation of ruthenium allenylidene complex.

Applications of Isolated Indenylidene-Ruthenium Complexes in ROMP... 

Two observations initiated a strong motivation for the preparation of indenylidene-ruthenium complexes via activation of propargyl alcohols and the synthesis of allenylidene-ruthenium intermediates. The first results from the synthesis of the first indenylidene complexes VIII and IX without observation of the expected allenylidene intermediate [42-44] (Schemes 8.7 and 8.8), and the initial evidence that the well-defined complex IX was an efficient catalyst for alkene metathesis reactions [43-44]. The second observation concerned the direct evidence that the well-defined stable allenylidene ruthenium(arene) complex Ib rearranged intramo-lecularly into the indenylidene-ruthenium complex XV via an acid-promoted process [22, 23] (Scheme 8.11) and that the in situ prepared [33] or isolated [34] derivatives XV behaved as efficient catalysts for ROMP and RCM reactions. 

Scheme 8.15 Preparation of indenylidene ruthenium complexes containing a NHC ligand.

Actually, applications of indenylidene-ruthenium complexes for alkene metathesis were reported before, at a time when the action mode of their ruthenium allenylidene precursors was not known. These complexes catalyzed a variety of RCM reactions of dienes and enynes [31, 32, 47] (see Section 8.2.2). 

The indenylidene-ruthenium complexes were shown to be the actual alkene metathesis catalysts arising from the addition of propargylic alcohols [15-18]. The Dixneuf group [19, 20] later revealed that the intramolecular rearrangement of allenylidene-ruthenium complexes into indenylidene-ruthenium complexes was... 

From Allenylidene to Indenylidene Ruthenium Complexes and Catalysts... 

A few weeks later, Nolan [16] reported the indenylidene-ruthenium complexes 7-10, which contain a NHC ligand analogous to the Grubbs II catalyst. Using catalysts 6 and 7 -10, excellent activities were shown in the RCM reaction of various... 

Once the NHC was introduced onto the ruthenium center, the addition of pyridine (10 equiv.) led to the 16-electron, monopyridine indenylidene complexes 54a-f (Scheme 14.24) [55, 56, 65, 66]. Interestingly, from a synthetic point of view, this preparation can also be achieved starting from (triphenylphos-phine)(indenylidene)ruthenium complexes, thereby avoiding the use of the costly and sensitive tricyclohexylphosphine [50,66]. The monopyridine complexes bearing mesityl substituents on the nitrogens were not very active at room temperature for the RCM of dienes and enynes, nor in the CM of methyl acrylate [66]. However, the controlled ROMP of norbornene-type monomers was allowed [65]. In contrast, the indenylidene complexes 54b and 54f, which bear 2,6-diisopropylphenyl substituents on the NHC and either a pyridine or 3-bromopyridine ligand, were... 

Indenylidene-ruthenium complexes as catalytic precursors arising from allenylidene-ruthenium complexes... 

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