research papers

Crystals of the

*β*-form of the title compound, 1,1,3,3-tetrafluoro-5,5-(2,2,3,3-tetrafluorotetramethylenedioxy)cyclotri(phosphazene), are triclinic,*P*, with lattice constants*a*= 12.392 (2),*b*= 16.569 (3),*c*= 19.257 (4) Å,*α*= 110.22 (3),*β*= 90.02 (3), γ = 97.10 (3)° and*V*= 3677.9 (12) Å^{3}with*Z*= 12, to yield*P*_{calc}= 2.010 Mg m^{−3}for*M*= 371.0 and_{r}*F*(000) = 2184. The structural data was refined to*R*= 0.0548 and*wR*= 0.0567 for 5536 observed reflections [|*F*| ≥ 3*σ*(*F*)] with a goodness-of-fit of 1.61 and a maximum residual of 0.47 e Å^{−3}. The six crystallographically independent molecules are all structurally equivalent, with approximately the same orientation for each molecule. The molecules are roughly arranged in layers lying parallel to the*ac*plane. Two types of these layers exist within the structure. Each layer exhibits approximate noncrystallographic symmetry elements. For layers at*y*~ and , the appropriate layer-group symmetry notation is*pc*2*a*, while the layer at*y*~ has idealized*p*2_{1}/*c*11 symmetry. The difference in the symmetries of the two types of layers arises from different sequencing of molecules with right- and left-handed chirality. Both layer groups require*β*to be equal to 90°, explaining its observed value. The structure can be described as a polytype structure, in which stacking faults occur every third layer. An*ABAABA*stacking pattern exists, where*A*corresponds to the layer at*y*= and while*B*corresponds to the layer at*y*= . In addition, successive layers are related by the following set of idealized translation vectorsSuperimposed upon these translation vectors is modulation of the chirality of the molecules.

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Crystallographic Information File (CIF) |

CCDC reference: 131879