Vinylidene and Propadienylidene Ligands

The chromium oxapropadienylidene complex affords dimethyl malonate when oxidized in methanol (77), and the diester is assumed to be produced by addition of the alcohol to the first-formed tricarbon dioxide  

If a mixture of diphenylacetylene and Mo[C(C1)=C(CN)2](CO)3( -C5H5) is heated, part of the cyanocarbon ligand is incorporated into the olive-green 6,6-dicyano-l,2,3,4-tetraphenylfulvene (72), which can be formed by cyclization of a C=C(CN)2 fragment with two molecules of alkyne (112)  

Finally, the stereospecific formation of tram-1,4-di-/-butylbuta-2,3-triene from HC=CBu, catalyzed by H2Ru(CO)(PPh3)3, suggests the interme- 

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