Dibenzouranocene and related compounds

Article abstract of DOI:10.1021/om50006a030

Bis(benzo[8-annulene])uranium(IV) (dibenzouranocene), 4, and the thorium analogue 5 have been prepared from benzocyclooctatetraene dianion and the metal tetrachlorides. The Diels-Alder product from cyclooctatrienyne and butadiene, 7,10-dihydrobenzocyclooctatetraene, 2, gave a uranocene derivative, 6, which could not be dehydrogenated to 4. Catalytic hydrogenation, however, did gave the uranium derivative 7 of tetrahydrobenzocyclooctatetraene. The corresponding deuterogenation gave 70% exo and 30% endo incorporation of deuterium. Reaction of cyclooctatetraene dianion with 1,4-dibromobutane gave cis-bicyclo[6.A.0]dodeca-2,4,6-triene, 8, which on deprotonation with KNH₂/NH₃ and treatment with UCl₄ also gave 7. Analysis of NMR spectra of 4 indicates a spin density distribution closely related to that in the radical anion of benzocyclooctatetraene. The ligand exchange equilibrium between 4 and uranocene has been determined and found to favor the mixed-sandwich compound.