Alkynyl-carbene ruthenium complex

With propargylic alcohols, in general, allenylidenes are formed. However, in the case of HC=CCMe2(OH), an intermolecular dimerization of the allenylidene ligands takes place to yield a vinylidene arbene complex. In the presence of base, this dimeric complex transforms into the corresponding alkynyl-carbene ruthenium complex. 

If cycloalkene-yne 65 having an o -alkynyl substituent at an olefinic position in a cycloalkene is treated with a ruthenium catalyst, what kinds of products are produced. In this reaction, ruthenium mono-substituted carbene complex XVII is anticipated to be formed from a highly strained ruthenacyclobutane intermediate. If it then reacts with ethylene, triene 67 should be formed, but if XVII reacts with an alkene part intramolecularly, bicyclic compound 66 should be formed via ruthenacyclobutane (Scheme 23). 

Not considered within this review are the wide range of porphyrin and other nitrogen macrocycle-stabilized ruthenium and osmium hydrocarbyl complexes. Readers should see the following as a starting point for information on this type of alkyl/aryl, alkynyl, vinylidene, allenylidene, and carbene complexes. 

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