The reaction of 3 molar equiv of o-fluorolithiobenzene with dicarbonyl(?5-cyclopentadienyl)iodoiron results in an intramolecular cyclization to give the metallacyclic product [(?5-C5H5)Fe(CO)(C6H 4-2-C-(O)-C6H4-2'-C6H 4-2?-F)]. Characterization was made by derivatization with tris(acetonitrile)tricarbonylchromium to give [(?5-C5H5)Fe(CO)(C6H 4-2-C(O)-C6H4-2'-C6H 4-2?-F)]-?6-Cr(CO)3 (3a). Compound 3a crystallizes in the monoclinic space group P21/c with lattice parameters a = 7.1633 (18) Å, b = 13.669 (6) Å, c = 24.116 (3) Å, ß = 95.763 (3)°, V = 2349.33 (12) Å3, ?(calc) = 1.584 g cm-3, and Z = 4. Least-squares refinement gave a final RF value of 0.065 for 1864 (I > 2.5s(I)) of 3071 unique reflections (Rw = 0.036, GOF = 2.08). © 1990 American Chemical Society.