Nickel-mediated cyclobutabenzene synthesis was proven to be useful in the stereoselective synthesis of trans-dibromocyclobutabenzene, bicyclobutabenzene and tricyclobutabenzene. The systems obtained were functionalized in four-membered rings and allow further transformation of these compds. This methodol. allows new entries to org. synthesis of polycyclic compds. and polymer chem. and to the prepn. of compds. relevant to the study of the Mills-Nixon effect. The crystal and mol. structure of of tris(tricarbonyliron)benzotricyclobutadiene were reported.