Propadienylidene Allenylidene Complexes

The first complexes to be described (16) were obtained from Fischer-type carbene complexes by successive reactions with a Lewis acid and a weak 

Attempts to prepare the dimethyl analog from HC=CCMe2(OH) led instead to the binuclear vinylidene-carbene complex (49) (72)  

The complex Mn[=C=CHC(OH)Bu2 ](CO)2(f/-C5H5) dehydrates in the mass spectrometer to give the parent ion of the corresponding propadienylidene complex, [Mn(=C=C=CBu2 )(CO)2(C5H5)]+ (26). 

The acylynolate anion (50) can be decarbonylated on irradiation, and subsequent deoxygenation (formal loss ofO2-) affords the propadienylidene complex (22). In some cases, this is not isolable or spontaneously polymerizes, but its intermediacy can be inferred from products obtained when the 

An alternative route to the dianionic ynolato complex is from propiolic ester complexes and excess organolithium reagents (21, 26, 27)  

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Complexes containing the unsaturated carbenes vinylidene (G and H) and propadienylidene (allenylidene) (I and J), and their cluster-bound analogs, are also known, although general routes to these reactive compounds have been discovered only within the last five years or so. Vinylidene, the simplest unsaturated carbene, has never been observed experimentally, as it undergoes an extremely fast 1,2-hydrogen shift to give acetylene ... 

Vinylidene and Propadienylidene (Allenylidene) Metal Complexes, 22, 59 X-Ray Structural Analysis of Organolithium Compounds, 24, 353 Ziegler-Natta Catalysis, 18, 99... 

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