Conformation cyclophosphazenes

The cyclophosphazene ring assumes a highly puckered conformation in both the zinc and aluminum complexes, indicating its remarkable flexibility to adapt to the coordination requirement of the metals. 

Fig. 10. Some of the ring conformations adopted by the eight membeied cyclophosphazene derivatives...

Structure, Conformation, and Basicity in Cyclophosphazenes and Related Compounds... 

The cyclophosphazene six-membered rings are quasi planar, as usual in this type of moiety. In fact, the distance from atoms to the best plane is lower than 0.056(3) A. In contrast, the SPIRO rings present a slight chair conformation... 

Lastly, the cyclophosphazene ring conformation is almost identical to that found in other similar structures. The NPN angles range between 113.0(1) and 120.5(2)°, while the P—N bonds range from 1.554(3) to 1.634(3) A. This is to be compared to the crystal structure of SPIRO N3P3C1JHN —(CH2)3 —NH]30) for example. 

Muller and coworkers have recently reported the molecular behavior of 1,3,5-trioxane in a cyclophosphazene inclusion compound using H-2 NMR [68]. The experimental data were obtained by variable-temperature line shape analysis, spin-spin and spin-lattice relaxation time measurements and by 2D exchange between 30 and 370 K. At room temperature, highly mobile trioxane guests were observed. They undergo various overall and conformational motions which give rise to substantial orientational disorder within the hexagonal cyclophosphazene channels. 

FIGURE 7.12 Ring conformations of cyclophosphazenes. (a) PjNjCl, (b) PjNjCIiq, (c) P4N4CIJ boat, (d) P4N4CI8 chair and (e) P4N4(NMe2)8. 

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