The Structure of a Dimer of a Derivative of Cyclobutadiene

In 1960 Kitahara, Caserio, Scardiglia and Roberts described the preparation of a dimer of fluorotriphenylcyclobutadiene (C_(22)H_(15)F)_2, (I), which they obtained by the action of phenyllithium on 1,1-difluoro-2,4-dichloro-3-phenylcyclobutene. Although dipole moment measurements, Raman spectra and nuclear magnetic resonance studies have since suggested that the substance might be anti-1,2-difluoro-3,4,5,6,7,8-hexaphenyl-tricyclo[4.2.0.0]octa-3,7-diene, other structures have not been ruled out absolutely. We are now completing an X-ray diffraction study of their material and can definitely confirm the stated structure.