Reactivity of Allenes towards Iron Carbonyl Complexes

A series of monosubstituted allenes was reacted with Fe2(CO)9 to give dinuclear iron-carbonyl complexes containing organic ligands derived either from monomeric or dimerized allene. A mechanism of formation is proposed based on isolated intermediates. These intermediates point to an allene dimerization via addition of a reactive allene iron complex to free allene. Unusual chemical shifts were observed for many resonances in the 1H- and 13C-NMR spectra of the new compounds.