A new polymorph of 1,3-bis(pentafluorophenyl)urea

The title compound, C13H2F10N2O, has been previously described in the space group Pbca with Z = 8 [Jai-nhuknan et al. (1997 ▶). Acta Cryst. C53, 455–457]. The current P212121 polymorph was obtained from a tetrahydrofuran solution. The pentafluorophenyl rings make dihedral angles of 50.35 (6) and 54.94 (6)° with the urea fragment, in close accord with those reported for the first polymorph. In the crystal, both of the N—H groups donate H atoms to the same carbonyl O atom, forming a one-dimensional molecular array along the a axis. There are close contacts between perfluorophenyl C atoms within the array [3.228 (3) Å] and halogen bonds are also observed between the arrays [F⋯F = 2.709 (2) and 2.7323 (18) Å].

The title compound, C 13 H 2 F 10 N 2 O, has been previously described in the space group Pbca with Z = 8 [Jai-nhuknan et al. (1997). Acta Cryst. C53,[455][456][457]. The current P2 1 2 1 2 1 polymorph was obtained from a tetrahydrofuran solution. The pentafluorophenyl rings make dihedral angles of 50.35 (6) and 54.94 (6) with the urea fragment, in close accord with those reported for the first polymorph. In the crystal, both of the N-H groups donate H atoms to the same carbonyl O atom, forming a one-dimensional molecular array along the a axis. There are close contacts between perfluorophenyl C atoms within the array [3.228 (3) Å ] and halogen bonds are also observed between the arrays [FÁ Á ÁF = 2.709 (2) and 2.7323 (18) Å ].

Experimental
The title compound was commercially purchased and recrystallized from a tetrahydrofuran solution.

Refinement
Friedel pairs were merged because the molecule itself was achiral and because there were not any anomalous scattering effects. The N-bound H atom was obtained from a difference Fourier map and was refined isotropically with the restriction of N-H range between 0.85 Å and 0.89 Å. U iso (H) values of the H atoms were set at 1.2U eq (parent atom).

Figure 1
The asymmetric unit of the title compound with atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres.

1,3-Bis(pentafluorophenyl)urea
Crystal data C 13 H 2 F 10 N 2 O M r = 392.16 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 4.5798 (7) Special details Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY Refinement. Refinement was performed using all reflections except for two with very negative F 2 . The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq F1