[(eta-5-C5H5)(CO)LFe = C = CH2] + CF3SO3- complexes react with phenylpropyne with formation of [2 + 2] cycloadducts [(eta-5-C5H5)(CO)LFe = activated C-C(Me) = C(Ph)-CH2] + CF3SO3 - (structurally characterized by X-ray crystallography); addition of phenyllithium leads to a stable cyclobutenyl complex in good yield.