The reactions of [Fe2(CO)9] with 2-exo,3-exo-bis(chloromethyl)-5,6-di(methylidene)-7-oxabicyclo[2.2.1]hep tane (5) and with 5,6-di(methylidene)-7-oxabicyclo[2.2.1]heptane-2-exo,3-exo-dimethyl bis(methanesulfonate) (6) afforded, together with the corresponding [exo-Fe(CO)3(1,3-diene)] complexes 7 and 8, the products of dimerization in the form of stable [Fe(CO)2{1,2,3-eta:6,7,8-eta)-octa-2,6-diene-1,8-diyl}] complexes 9 and 10, respectively, with high stereoselectivity. The structure of 10 was established by means of single-crystal X-ray diffraction.