Carbon-carbon bond forming and cleavage in the reactions of isopropenyl-acetylene and 2-methyl-hex-1-en-3-yne with Fe3(CO)12 in basic methanolic solution.The X-ray structure of Fe2(CO)5[mu-eta7-(RCC(H)C(CH3)CR)] (R= CH3(=CH2))

The title complex is the main product of the reaction of Fe3(CO)12 with isopropenylacetylene in basic methanolic solution (followed by acidification); it is obtained upon carbon–carbon bond forming and dimerization of the alkyne. The same complex is also obtained by reacting Fe3(CO)12 in CH3OH/KOH solution with 2-methyl-hex-1-en-3-yne; carbon–carbon bond cleavage presumably occurs to form isopropenylacetylene, which then reacts with the iron carbonyl. The unprecedented structure of the complex has been determined with a X-ray diffraction analysis.