Crystal structures of three hexakis(fluoroaryloxy)cyclotriphosphazenes

The syntheses and crystal structures of three cyclotriphosphazenes, all with fluorinated aryloxy side groups that generate different steric characteristics, viz. hexakis(pentafluorophenoxy)cyclotriphosphazene, N3P3(OC6F5)6, 1, hexakis[4-(trifluoromethyl)phenoxy]cyclotriphosphazene, N3P3[OC6H4(CF3)]6, 2 and hexakis[3,5-bis(trifluoromethyl)phenoxy]cyclotriphosphazene, N3P3[OC6H3(CF3)2]6 3, are reported. Specifically, each phosphorus atom bears either two pentafluorophenoxy, 4-trifluoromethylphenoxy, or 3,5-trifluoromethylphenoxy groups. The central six-membered phosphazene rings display envelope pucker conformations in each case, albeit to varying degrees. The maximum displacement of the 'flap atom' from the plane through the other ring atoms [0.308(5)Å] is seen in 1, in a molecule that is devoid of hydrogen atoms and which exhibits a 'wind-swept' look with all the aromatic rings displaced in the same direction. In 3 an intramolecular C - H(aromatic)⋯F interaction is observed. All the -CF3 groups in 2 and 3 exhibit positional disorder over two rotated orientations in close to statistical ratios. The extended structures of 2 and 3 are consolidated by C - H⋯F interactions of two kinds: (a) linear chains, and (b) cyclic between molecules related by inversion centers. In both 1 and 3, one of the six substituted phenyl rings has a parallel-displaced aromatic π-π stacking interaction with its respective symmetry mate with slippage values of 2.2Å in 1 and 1.0Å in 3. None of the structures reported here have solvent voids that could lead to clathrate formation.