The gas-phase ion chemistry between a series of Fe(arene)(+) ions and halobenzene and dihalobenzene species was studied. Fe+ in the arene complex acts as a reaction-initiating center to insert oxidatively into the phenyl-X bond (X = Cl, Br, I), The arene ligand then undergoes migratory insertion into the Fe+-phenyl sigma bond. Subsequent hydrogen abstraction from the organic moiety and HX elimination generate Fe(biphenyl)(+) ions. This reaction cycle may be repeated up to five times to give Fe(polyphenyl)(+) in contrast, Fe(fluorobenzene)(+) shows no reactivity with chlorobenzene, while CH3 groups on the arene ligand sterically hinder the migratory insertion into the Fe+-phenyl bond.