Reactions Supposed to Proceed via Metal Vinylidene Complexes

Reactions Supposed to Proceed via Metal Vinylidene Complexes 

Many stoichiometric reactions, usually involving alkynes, have been reported to proceed via metal vinylidene complexes which have not been detected nor isolated. This section does not survey the extensive field of reactions catalyzed by metal vinylidene complexes. 

The reactions are those of functionalized 1-alkynes, the first of which were described for alkynes bearing substituted hydroxymethyl groups, such as substituted propargyl alcohols, HC=CCRR (OH), and often proceed further to form metal allenylidene complexes, by spontaneous dehydration of a (usually unobserved) hydroxy-vinylidene complex (Equation 1.22)  

Reactions of propargylic alcohols HC=CCHR(OH) (R= H, Me) with RuCl(L)2Cp  

Formation of metal acyl or carbonyl complexes from 1-alkynes in the presence of water is often assumed to proceed via attack on an intermediate vinylidene complex to give a hydroxycarbene complex (Equation 1.24)  

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