The blue crystalline compound isolated from the benzotrifuroxan–triphenylphosphine reaction has been shown to be 8,8′-bis(triphenylphosphoranylidene)bi(benzo[1,2-c:4,5-c′]difurazan-4-ylidene) by three-dimensional X-ray structural analysis. The central heterocyclic system is overcrowded and not planar. Each of the C₆ rings is boat-shaped although the individual carbon atoms are trigonal planar. The average value of the carbon–carbon bond length in this system 1.46 Å is significantly longer than in a benzenoid system. Other mean bond lengths are PC 1·74, CN 1·32, and N-O 1·40 Å.