The ‘yellow compound’ isolated from the reaction of benzotrifuroxan with triphenylphosphine has been shown to be 1,3,5-trinitro-2,4,6-tris(triphenylphosphoranylideneamino)benzene, together with toluene of crystalisation, by three-dimensional X-ray structure analysis. The central C₆ ring is benzenoid and the planes of the nitro-groups are approximately at right angles to it. In the triphenylphosphoranylideneamino-groups the P–N bonds, mean 1.56 A, are short and the N–C bonds, mean 1.34 Å, are shorter than the O₂N–C bonds, mean 1.49 Å, suggesting considerable electron delocalisation over the 2,4,6-tris(triphenylphosphoranylideneamino)benzene grouping.