Dimorphism in 4,4,6,6-tetrachloro-2,2-(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene and 6,6-dichloro-2,2:4,4-bis(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene.

A second, polymorphic, form of the previously reported compound 4,4,6,6-tetrachloro-2,2-(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene, C(5)H(10)Cl(4)N(3)O(2)P(3), is now reported. The molecular structures of these two compounds are similar, aside from minor conformational differences. However, the compounds crystallize in two different space groups and exhibit quite different crystal structure assemblies. Additionally, 6,6-dichloro-2,2:4,4-bis(2,2-dimethylpropane-1,3-dioxy)cyclotriphosphazene, C(10)H(20)Cl(2)N(3)O(4)P(3), is shown to exhibit two different conformational polymorphs when crystallized from different solvent mixtures. The alpha form crystallizes in the space group Pnma with the molecular structure lying on a mirror plane (symmetry code: x, -y + {1/2}, z), whilst the beta form is in the space group C2/c with the molecular structure lying on a twofold axis (symmetry code: -x, y, -z + {3/2}). The difference between the two molecular structures is in the conformation of the spiro-ring substituents with respect to the phosphazene ring. The resulting crystal structures give rise to differing packing motifs.