Ruthenium intramolecular rearrangement

Among the R2C(=C) =Ru homologs promoting alkene metathesis the most recent discoveries deal vhth the allenylidene-ruthenium and related pre-catalysts. This chapter is devoted to the class of ruthenium-allenylidene metathesis precatalysts, their intramolecularly rearranged indenylidene catalysts, and their use in... 

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... 

Dixneufs group [19, 20] has reported the intramolecular rearrangement of a ruthenium-bound allenylidene ligand into an indenylidene ligand. The stoichiometric protonation of arene-ruthenium-allenylidene complexes lla-c with TfOH at -40 °C gave the alkenyl carbyne complex 12, which, upon raising the temperature to -20 °C, completely transformed into the related, isolable arene-ruthenium, indenylidene complexes 13a-c (Scheme 14.6). The protonation of the allenylidene carbon at C2 generates a very electrophilic carbyne carbon at... 

The homobimetallic, ethylene-ruthenium complex 15, which contains three chloro bridges, was readily obtained from the reaction of [RuCl2(/ -cymene)]2 with 1 atm of ethylene [34]. In 2009, Demonceau and Delaude [34] showed that complex 15 could be a useful precursor to allow subsequent access to the diruthenium vinylidene complex 16, allenylidene complex 17, and indenylidene complex 18 (Scheme 14.8). Upon reaction with propargylic alcohol, complex 15 afforded vinylidene complex 16, which converted into the allenylidene complex 17 in the presence of molecular sieves [34]. As shown in the acid-promoted intramolecular rearrangement of mononuclear ruthenium allenylidene complexes [19, 20, 32], the addition of a stoichiometric amount of TsOH to complex 17 at -50 °C led to the indenylidene binuclear complex 18 [34]. Complex 18 has been well... 

Ruthenium and Osmium.—Square-pyramidal compounds [M(X)(Y)(PPh3)3] exhibit a dynamic process in solution which according to P n.m.r. spectroscopy equilibrates apical and basal phosphine sites. The measured values of A5 (Table 5) are consistent with this being an intramolecular rearrangement (probably Berry pseudorotation) and since addition of PPh3 does not effect the process a bimolecular exchange is also excluded. 

Intramolecular Rearrangements of Tris-chelate Complexes.— Recently there has been considerable attention paid to the stereochemical non-rigidity of tris-chelate complexes and a number of reviews have dealt with the subject. Studies of NN-disubstituted dithiocarbarmato-complexes of the type [M(R R -dtc)8] (R, R = alkyl or aryl) have been extended and the results for intramolecular metal-centre inversion (probably by the Bailar trigonal-twist mechanism) are summarized for ruthenium(m) complexes in Table 29. The low values of AG and are surprising for ruthenium(m) since previous studies indicated that tris-chelates of this... 

NMR of 7a with TfOH showed that at -40°C complex 7a led to the formation of an alkenylcarbyne complex 32 by protonation of the aUenylidene P-carbon (Scheme 22). This species was found to be catalytically inactive for a test RCM reaction. On rising the temperature to -20°C the species 32 releases its proton and afforded the indenyhdene-ruthenium complex 33 that could be further isolated. The complex 33 resulted from an intramolecular rearrangement and was revealed as the active species (Scheme 22) die complex 33 was identified to the species formed from 7a on thermal reaction. 

Rearrangement of the ruthenium (diaminocarbene) isocyanide complex 28 has been noted above. Migration of the carbene substituent group is thought to occur via an intramolecular cyclization reaction (57,58) ... 

The first hydration step was promoted by Bronsted acids containing weakly or noncoordinating anions. In the second step, an intramolecular hydrogen transfer in the secondary alcohol was catalyzed by ruthenium(III) salts with chelating bipyridyl-type ligands. The possible complexation of the latter with the diene did not inhibit its catalytic activity in the allylic rearrangements, under acid-catalyzed hydration conditions. 

Increased reactivity toward nucleophiles may render the five-membered cyclic sulfates unstable, for instance, because of an intramolecular nucleophilic attack <1997J(P1)3173>. Thus, when the sulfate 44 is prepared by oxidation of the corresponding sulfite with ruthenium tetroxide, it undergoes a clean rearrangement at room temperature to the isomeric six-membered cyclic sulfate of 2-benzoyloxypropane-l,3-diol (Scheme 5) <1997J(P1)3173>. 

---