The reaction of allenes with enneacarbonyldi-iron results in the formation of binuclear complexes. Details of the crystal and molecular structure of the product of the reaction between a cyclic C11-allene and enneacarbonyldi-iron are presented. The complex crystallises in the triclinic system with a unit cell of dimensions, a= 10·39, b= 8·33, c= 14·62 Å, α= 102° 10′, β= 110° 25′, and γ= 114° 58′. It contains an allylic group of carbon atoms with C–C bond lengths of 1·41 and 1·42 Å and an internal angle of 114·6°. One iron atom, which is bonded to three carbonyl groups, is π-bonded to this group at a distance of 1·96 Å from the central allylic carbon atom and 2·20 and 2·17 Å from the other two allylic carbon atoms. The second iron atom, which is bonded to the remaining four carbonyl groups, is σ-bonded to the central allylic carbon atom at a distance of 2·02 Å. The two iron atoms are linked by a metal–metal bond of length 2·65 Å.